PITUITARY HORMONES AND THEIR HYPOTHALAMIC

PITUITARY HORMONES
AND THEIR HYPOTHALAMIC RELEASING HORMONES
A synopsis of hormones and their pharmacological importance:
A. ANTERIOR PITUITARY HORMONES
 GH (somatropin) – for GH deficiency (in children – dwarfism; in adults)
– for growth retardation (in chr. renal disease), cahexia (AIDS)
GH-antagonist: pegvisomant – for GH excess (gigantism, acromegaly), as a subst. for SST-anal.
 Prolactin – with no therapeutic use
Related: – D-receptor antagonists: cause hyperprolactinemia as an unwanted effect
– D-receptor agonists (bromocriptine, pergolide, quinagolide, cabergoline):
are used to treat GH excess (gigantism, acromegaly) and hyperprolactinemia
 FSH – to induce follicle development in anovulatory women, and for in vitro fertilization (IVF)
 LH – together with FSH, to induce spermiogenesis (after androgen and hCG) in infertile men
Related: hCG – detected by pregnancy tests, measured to assess pregnancy progression
– to induce ovulation (after FSH treatment) in anovulatory women, and for IVF
– to induce testosterone synthesis (after androgen treatment) in infertile men
– to maintain spermiogenesis (after androgen, hCG, FSH+LH) in infertile men
– to induce testicular descent in cryptorhidism
 TSH – with no medical use
 ACTH – only for diagnostic use; analogue: cosyntropin (24 aa) – only for diagnostic use
B. HYPOTHALAMIC REALEASING HORMONES
 GHRH (sermorelin) – for GH deficient children (dwarfism),
as a substitute for GH (somatropin, somatrem)
Related: Somatostatin; SST-analogues: octreotide, lanreotide, seglitide, vapreotide
– for GH excess (gigantism, acromegaly), as substit for D-rec agonists or pegvisomant
– for TSH excess (thyrotrope adenoma); VIP- or 5HT-secr. GI tumors (e.g., carcinoid)
– for inflammatory diseases (e.g., inflammatory bowel disease, rheumatoid arthritis)
 GnRH (gonadorelin) – short acting, only for diagnostic use
GnRH analogues – 1: GnRH receptor agonists: leuprolide, goserelin
Repeatedly given down-regulate GnRH receptor  FSH, LH = pharmacological castration
– for gonadotropin-dependent precocious puberty
– for sex steroid dependent tumors (prostate cancer, breast cancer)
– for sex steroid responsive other disorders (endometriosis, uterine leiomyoma, a. i. porphyria)
GnRH analogues – 2: GnRH receptor antagonists: cetrorelix, ganirelix, abarelix
Acutely given inhibit GnRH receptors  FSH, LH = pharmacological castration
– for sex steroid dependent tu (prostate cancer, breast cancer), as substitutes for agonists
– for blocking premature ovulation in FSH-treated women whose ova will be used for IVF
 TRH – with no medical use
 CRH – only for diagnostic use
C. POSTERIOR PITUITARY HORMONES
 Oxytocin – for induction of labor (low dose rate), for postpartum uterine bleeding (high dose)
 Vasopressin, ADH: V1 and V2 rec agonist – for V1 rec (in smooth muscle) activation only in
postop. ileus, bleedings (esophagus), vasoregulatory shock, as vasoconstrictor with l. anesth.
Desmopressin – selective agonist on V2 receptors (in renal collecting duct cells):
– for central diabetes insipidus (CDI; decreased ADH secretion)
– for inducing water retention in other disorders (enuresis nocturna, post lumbar punction)
– for inducing vW factor and VIII factor synthesis in vW disease (type I) and in hemophilia A
Related: renal diabetes insipidus (RDI; decreased ADH effect; e.g. V2 receptor mutation)
Drugs useful in RDI: thiazide diuretics, amiloride (if Li-induced), indomethacine
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A. ANTERIOR PITUITARY HORMONES
AND THEIR HYPOTHALAMIC REGULATORY HORMONES
PVN = Paraventricular nucleus
ARC = Arcuate nucleus
Somatostatin and dopamine
are negative regulators!
ARC = Arcuate nucleus
CELLS OF THE
ANTERIOR PITUITARY:
 Somatotropes  GH
 Lactotropes  Prolactin
 Gonadotropes  FSH, LH
 Corticotropes  ACTH
 Thyrotropes  TSH
Protein Hormones of the Anterior Pituitary and Placenta
HORMONE
I. Somatropic hormones (monomeric proteins)
 Growth hormone (GH)
 Prolactin (PRL)
 Placental lactogen (PL)
AMINO ACID RESIDUES
191
199
190
II. Glycoprotein hormones (heterodimeric with common -subunit)
 Luteinizing hormone (LH)
-92,
 Follicle-stimulating hormone (FSH)
-92,
 Thyroid-stimulating hormone (TSH)
-92,
 Human chorionic gonadotropin (hCG)
-92,
III. POMC-derived hormones
 Corticotropin (ACTH)
 -Melanocyte-stimulating hormone (-MSH)
-121
-111
-118
-145
39
13
POMC = Pro-opiomelanocortin
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GROWTH HORMONE (GH)
REGULATION OF GH SECRETION:
GH secretion is increased by:
 GHRH (GHRHrec  Gs  AC  cAMP)
 Ghrelin (hunger-stimulating peptide released
from the stomach and the pancreas)
GH secretion is decreased by:
 IGF (negative feedback)
 Somatostatin (SSTrecGiACcAMP)
MAIN EFFECTS OF GH – direct, indirect (trough IGF), both direct and indirect
 Direct GH effects:  lipolysis, glycogenolysis: blood glucose (diabetogenic effect)
 Effects trough IGF:  blood glucose (by glucose uptake –- insulin-like effect)
 Both direct and indirect effects: increased growth in BONE ( longitudinal
growth;  BMD) and MUSCLE ( muscle mass)
MECHANISM OF GH ACTION: via GH receptor – JAK – STAT pathway –  expr. of IGF-1
 Pegylated GH,
GH antagonist
JAK Janus kinase
STAT Signal
transducer and
activator of
transcription (a
transcription factor)
IRS Insulin receptor
substrate
PI3K Phosphatidyl
inositol 3-kinase
SHC Src homology2 containing protein
MAPK Mitogenactivated protein
kinase
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GH DEFICIENCY AND ITS TREATMENT
GH deficiency:
Cause: typically hypothalamic, i.e. GHRH secretion (rarely pituitary injury by radiation or disease)
Symptom: in children: growth deficit = pituitary dwarfism; in adults:  muscle mass,  fat mass
Diagnosis: by provocative tests (e.g., insulin-induced hypoglycemia increases serum GH levels)
Treatment options of GH deficiency - by administration of recombinant hormones:
1. GH (somatropin) – used in most cases
2. IGF-1 (mecasermin) – less effective in stimulating bone growth than GH
– used in Laron dwarfism (mutant GH receptor) or in rare IGF deficiency
3. GHRH (sermorelin) – less effective than GH; ineffective in pituitary defect of GH secretion
– has been withdrawn from US market
GH treatment:
GH preparations (produced in E. coli by recombinant DNA technology):
 Generic name: Somatropin = rhGH. (M.w. = 22 kDa)
 Marketed under various trade names.
GH formulations:
 Short-acting injectable solutions, given daily: - for s.c. injection (in prefilled syringe)
- for non-needle injection systems
 Long-acting microencapsulated depot inj. (NUTROPIN DEPOT) – given i.m., monthly or biweekly
GH pharmacokinetics:
 Elimination mechanism: degradation into amino acids (largely in the kidneys)
 Elimination T1/2: ~30 minutes
 Duration of action of the s.c. dose: 12-48 hrs
GH indications:
1. For GH-deficient children
- Dose: 25-50 µg/kg/day
- The initial response is monitored by measuring serum IGF-1 levels
- Duration of GH treatment: as long as the patient is responsive, or until epiphyses are fused.
Some even continue in early adulthood to assist bone mineralization.
2. For GH-deficient adults (hypothalamic or pituitary disease, injury, surgery, radiation therapy)
3. Chronic renal disease-associated growth retardation in children
4. AIDS-associated wasting (cahexia)
Controversial or unaccepted GH indications (effectiveness is not validated):
 For elderly, to ameliorate or reverse age-related decline in physical condition
 For athletes, to increase muscle strength and performance (GH use violates regulations)
GH-induced adverse effects:
In children:
 Idiopathic intracranial hypertension. Signs: papilledema, visual changes, headache, nausea.
Occurs within the first 2 months of GH therapy (perform funduscopic examination periodically!)
 Skeletal problems: scoliosis, slipped capital femoral epiphysis – if growth is too rapid
 Diabetes mellitus – GH  hormone-sensitive lipase (in adipose tissue)   FFA in plasma
  FFA oxidation in muscle   glucose uptake by the muscle
 Leukemia – anecdotal cases; causative relationship has not been established
In adults:
 Peripheral edema
 Pain: arthralgia, myalgia, neuropathy, e.g. carpal tunnel sy (median nerve neuropathy at the wrist)
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GH EXCESS AND ITS TREATMENT
GH excess:
Cause: pituitary micro- or macroadenoma
Symptom: if epiphyses are unfused  gigantism
if epiphyses are fused  acromegaly
Diagnosis: high serum GH or IGF-1 levels; glucose (75 g p.os) fail to suppress serum GH levels
Treatment options of GH excess:
A. Non-drug treatment: removal of the adenoma by surgery or pituitary irradiation
B. Drug treatment: 1. Somatostain (SST) analogues, e.g. octreotide to  GH secretion
2. Dopamine-receptor agonists, e.g. cabergoline to  GH secretion
3. GH antagonist: pegvisomant to block GH action on GH receptors
1. Somatostain (SST) analogues (agonists on SST receptors):
 Structures of somatostatins and clinically available analogs (octa- or hexapeptides):
Somatostatin-28 (Prosomatostatin):
Ser-Ala-Asn-Ser-Asn-Pro-Ala-Met-Ala-Pro-Arg-Glu-Arg-Lys-Ala-Gly-Cys-Lys-Asn-Phe-Phe-Trp-Lys-Thr-Phe-Thr-Ser-Cys
Ala-Gly-Cys-Lys-Asn-Phe-Phe-Trp-Lys-Thr-Phe-Thr-Ser-Cys
Somatostatin-14:
Octreotide:
D-Phe-Cys-Phe-D-Trp-Lys-Thr-Cys-Thr-ol
Lanreotide:
D-Nal-Cys-Tyr-D-Trp-Lys-Val-Cys-Thr-NH2
Vapreotide:
D-Phe-Cys-Tyr-D-Trp-Lys-Val-Cys-Trp-NH2
Seglitide:
N-Methyl-Ala-Tyr-D-Trp-Lys-Val-Phe
 Effects of SST and analogues (e.g., octreotide):
They activate SST rec  Gi  AC  cAMP  K+ ch opening (hyperpolarization), therefore
- Inhibit the release of - GHRH (from the arcuate nucleus neurons in the hypothalamus), and
- GH (from somatotropes in the pituitary)
- Inhibit other secretions (e.g., TSH, insulin, VIP-secreting tumors, 5HT-secreting carcinoid;
secretion of cytokines from inflammatory cells)
 Preparation of SST analogues:
- Short-acting preparations (s.c. injections): Octreotide (SANDOSTATIN)
T1/2 = 90 min, duration of action 12 hrs, dose 3x100 µg/day sc.
- Long-acting preparations (i.m. injections):
- Slow release form of octreotide (SANDOSTATIN LAR DEPOT): once every 4 weeks, i.m.
- Lanreotide (SOMATULINE LA): once every 2 weeks, i.m.
 Indications of SST analogues – to decrease secretion of hormones or cytokines in:
1. Pituitary adenoma overproducing GH (in acromegaly patients)
 SST analogue is expected to GH, IGF-1 levels;  pituitary tumor size (by  GHRH secr.)
2. Pituitary adenoma overproducing TSH (i.e., thyrotrope adenoma)
3. GI tumors secreting VIP or 5HT (e.g., carcinoid)
Octreotide alleviates watery diarrhea (caused by VIP), flushing and diarrhea (caused by 5HT).
4. Treatment of some inflammatory diseases (e.g., inflammatory bowel disease, rheum. arthr.)
5. Treatment of sulfonylurea (e.g., glipizide) intoxication: octreotide suppresses insulin secretion
 Adverse effects: GI (diarrhea, nausea, abd. pain), gall bladder sludge/stone, hypothyroidism
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2. Dopamine-receptor agonists, e.g. cabergoline:
Paradoxically, D receptor agonists GH secretion in some patients with acromegaly.
(D receptor agonists are also used in prolactinoma and Parkinson’s disease.)
3. GH antagonist: pegvisomant (SOMAVERT):
 Chemistry: a rhGH molecule modified by covalent addition of polyethylene glycol (PEG) chains
 Action: pegvisomant binds to the GH receptor, but does not activate it.
 Indication: for acromegalic patients not responding to SST analogs
 Elimination: slow due to pegylation; T1/2 ~6 days
 Dose: - Loading: 40 mg s.c.
- Maintenance: 10 mg/day s.c.
 Monitoring: by measuring serum IGF-1 levels in 4-week intervals (they should be normalized)
 Unwanted effect: antibody formation
Note: Another pegylated protein used as drug is PEG-asparaginase that is used for treatment of
acute lymphoid leukemia. Pegylation increases the T1/2 of asparaginase from 15 hrs to 15 days!
PROLACTIN (LTH)
REGULATION OF PROLACTIN SECRETION:
Secretion from:
1. Lactotrope cells of the anterior pituitary
2. Decidual cells of the endometrium
 in the luteal phase of menstrual cycle
 in pregnancy  prolactin in amniotic fluid
1. Inhibitory regulation by dopamine:
 Released: from arcuate nucleus neurons
(i.e., tuberoinfundibular neurons)
 Acts: via D2 receptors on lactotropes
 Gi  AC  cAMP
2. Stimulators:
 Physiological: suckling,
breast manipulation
 Non-physiological:
elevated TRH (in hypothyreosis)
 hyperprolactinemia, galactorrhea
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MAJOR EFFECTS OF PROLACTIN:
1. BREAST: prolactin prepares the breast for lactation by inducing growth and differentiation of
mammary epithelium (ductal and lobuloalveolar cells)
2. OTHER SITES (liver, kidney, testes, ovary, immune cells) – with uncertain significance
MECHANISM OF PROLACTIN ACTION:
Acts on prolactin receptors, which work like GH receptors (see figure).
Prolactin binding  altered receptor conformation  recruitment of JAK  STAT phosphorylation
Target genes: Milk proteins (e.g., caseins); intracellular structural proteins (e.g., keratins);
extracellular signaling proteins (e.g., amphiregulin, Wnt4), etc.
THERAPEUTIC USE OF PROLACTIN: none
HYPERPROLACTINEMIA – Causes, symptoms, treatment
Causes:
1. DISORDERS: Prolactinoma (pituitary micro- or macroadenoma)
Others: primary hypothyroidism (TRH secr); renal failure (TRH elimination)
2. DRUGS: centrally acting dopamine-receptor antagonists and dopamine-depletors, such as
 Antipsychotics: phenothiazines, e.g. trifluoperazine; butyrophenones, e.g. haloperidol
 Prokinetics: metoclopramide
 DA depletors: alpha-methyldopa, reserpine
Symptoms:
 In both sexes: - Gynecomastia, (galactorrhea);
Loss of libido, infertility (because prolactin inhibits GnRH secretion)
 In women:
- Amenorrhea, anovulation
 In men:
- Impotence (erectile dysfunction)
D2-receptor agonists for prolactinoma-induced hyperprolactinemia:
Drugs (bromocriptine and cabergoline are ergot derivatives; these are D2 and 5HT2 agonists):
Bromocriptine
Quinagolide
Cabergoline
T1/2
Dose
5 hrs 3 x 2.5 mg/day
25 hrs 1 x 2.5 mg/day
65 hrs 2 x 0.25 mg/week
Specific feature
F = 7%, hepatic biotransformation + biliary excret.
non-ergot derivative, D2 agonist only
greater D2-selectivity; less nausea
Therapeutic effects:
1. Normalization of serum prolactin levels
2. Decrease in tumor size (however, they do not cure prolactinomas!)
3. Normalization of ovulation, restoration of fertility
(most patients may become pregnant; these drugs are reasonably safe during pregnancy)
Adverse effects – result from D2 receptor activation (1, 2) or 5HT2 receptor activation (3-5)
1. Nausea, vomiting
2. Postural hypotension, nasal congestion
3. Digital vasospasm (Raynaud phenomenon)
4. CNS effects: psychosis, hallucinations, nightmares, insomnia
5. Fibrosis (e.g. cardiac, pleuropulmonal) after long-term use. These drugs activate the 5-HT2B
receptors of cardiac valvular fibroblasts, causing proliferative valve disease. Other 5-HT2B agonists
(ergotamine, methysergide, fenfluramine, and 5-HT in carcinoid sy) may also cause such disorder.
Other uses: 1. Acromegaly – in higher doses (because DA also decreases GH secretion)
2. Parkinson’s disease – in even higher doses
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GONADOTROPIN RELEASING HORMONE (GnRH) and
GONADOTROPINS (LH, FSH, hCG)
REGULATION OF GONADOTROPIN SECRETION:
SECRETION OF GnRH, LH and FSH
– some important points:
 GnRH (a decapeptide) controls both FSH and
LH secretions. Thus: GnRH = FSH-RH = LHRH
GnRH is released intermittently under control of
a pulse generator at the arcuate nucleus, which
becomes active at puberty (particularly during
the sleep period).
 GnRH acts on GnRH receptors located on
gonadotropes (Gq  PLC  IP3  Ca2+).
GnRH receptors are desensitized and
down-regulated upon continued administration
of GnRH or its analogs.
 LH (and hCG) acts on LH receptor, whereas
FSH acts on FSH receptor. (Both work via
Gs  AC  cAMP, but at higher levels also
via Gq  PLC  IP3  Ca2+).
 Sex steroids feedback-inhibit the secretion of
both GnRH and gonadotropins (yet the
ovulationary surge in estrogens stimulates FSH
secretion).
 Inhibins, peptides of the TGF family, are
made in both the ovary (granulosa cells) and
the testes (Sertoli cells) and inhibit FSH
secretion (but not LH secretion).
EFFECTS OF GONADOTROPINS:
IN MEN
Targets testicular Sertoli cells
FSH  nutrient production
for spermiogenesis
LH*
Targets testicular Leydig cells
 testosterone synthesis
 - spermiogenesis,
- libido,
- secondary sexual ch.
IN WOMEN
 Induces ovarian follicle development
 LH receptor expression on theca and granulosa cells
 Estrone and estradiol synthesis from androstendione
in the granulosa cells by inducing aromatase
 Induces ovulation (rupture of the dominant follicle)
 Androstendione synthesis by the theca cells ( E2)
 Progesterone synthesis by the corpus luteum
* hCG has LH-like effects
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USES OF GnRH AND ITS ANALOGS (GnRH receptor agonists, antagonists):
AMINO
ACID
RESIDUE
1
2
3
4
5
6
7
8
9
10
Gly-NH2
FORM
Agonists (Others than below: Buserelin, Nafarelin, Desorelin, Historelin, Triptorelin)
PyroGlu
His
Trp
Ser
Tyr
Gly
Leu
Arg
Pro
Leuprolide
------------
--------
-------
----
-------------
D-Leu
-----
--------------
Pro-NHEt
Goserelin
------------
--------
-------
----
-------------
D-Ser(tBu)
-----
--------------
------------
AzGly-NH2
SC, IP
Cetrorelix
Ac-D-Nal
D-Cpa
D-Pal
----
-------------
D-Cit
-----
--------------
------------
D-Ala-NH2
SC
Ganirelix
Ac-D-Nal
D-Cpa
D-Pal
----
-------------
D-hArg(Et)2
-----
D-hArg(Et)2
------------
D-Ala-NH2
SC
Lys(iPr)
------------
D-Ala-NH2
SC, D
GnRH
IV, SC
IM, SC, D
Antagonists
Ac-D-Nal D-Cpa D-Pal ---- Tyr(N-Me)
D-Asn
----Abarelix
D = depot, IP = implant, Nal, Pal and Cpa are derivatives of alanine.
I. GnRH – USED ONLY FOR DIAGNOSTIC PURPOSE:
Synthetic GnRH (gonadorelin) is a decapeptide with a short T1/2 (3 min), therefore it is used only
to determine the cause of hypogonadotropic hypogonadism (i.e., hypothalamic or pituitary defect).
II. GnRH ANALOGS – USED ONLY FOR THERAPEUTIC PURPOSE:
Properties: - have prolonged action (D-amino acids at #6 and #10 slow their degradation)
- have enhanced potency
- fall into 2 groups: A. GnRH receptor agonist, B. GnRH receptor antagonists
A. USES OF GnRH RECEPTOR AGONISTS (e.g., leuprolide, goserelin):
 When given repeatedly, agonist GnRH analogues down-regulate GnRH receptors
 decrease FSH and LH secretion
 decrease secretion of gonadal steroids = PHARMACOLOGICAL CASTRATION
 Indications:
1. Gonadotropin-dependent precocious puberty
2. Sex steroid dependent tumors
- Prostate cancer (to decrease testosterone production; prostate cancer is androgen-dependent)
- Breast cancer (to decrease estradiol production; breast cancer may be estrogen-dependent)
3. Sex steroid responsive other conditions:
Uterine disorders (endometriosis, uterine leiomyomas); acute intermittent porphyria
 Adverse effects:
1. Transient stimulation of tumor growth (prostate, breast) caused by agonistic effect of GnRH
analogues on GnRH receptors ( sex steroid synthesis) before the receptors become downregulated. For example, in patients with vertebral metastases increased tumor growth may
cause spinal cord compression and paralysis. In this condition, use a GnRH antagonist (e.g.,
extended release abarelix) instead!
2. Signs of estrogen deficiency: hot flushes, vaginal atrophy, decreased bone mineral density
B. USES OF GnRH RECEPTOR ANTAGONISTS (directly cause pharmacological castration)
 Indications:
1. Sex steroid dependent tumors (see above), instead of the agonist GnRH analogues. Unlike the
agonists, the antagonists do not cause transient stimulation of tumor growth.
2. To suppress LH secretion and resultant premature ovulation in FSH-treated women whose ova
will be used for in vitro fertilization (IVF; assisted reproductive technology). Later, hCG is given
to induce final oocyte development and ovulation. Then ova are retrieved for in vitro fertilization.
 Adverse effects: Signs of estrogen deficiency (see above), hypersensitivity reaction
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USES OF GONADOTROPINS (FSH, LH, hCG)  diagnostic and therapeutic
I. DIAGNOSTIC ASSAYS OF GONADOTROPINS with the following objectives:
1. Diagosis of pregnancy - assays immunologically detect or measure hCG in urine or plasma
 Qualitative assays: detect hCG in urine within a few days after the first missed menstrual
period (commercial pregnancy test kits)
 Quantitative assays: measure hCG in plasma to assess if pregnancy proceeds normally, or
to detect ectopic pregnancy, hydatidoform mole, or choriocarcinoma.
2. Timing of ovulation: Over-the-counter kits are used to detect LH increase in urine. LH surge
occurs 12 hrs before ovulation. This assists in timing the intercourse to achieve pregnancy.
3. Diagnosis of male or female reproductive diseases with RIA for LH and FSH in plasma
 Hypogonadotropic hypogonadism: low levels of LH and FSH (hypothal or pituitary cause)
 Primary gonadal disease causing hypogonadism: high levels of LH and FSH
 Reduced fertility in women: FSH level is high (≥10 mIUml; indicating low estrogen production)
 Leydig cell failure in men: hCG administration barely increases serum testosterone levels
II. THERAPEUTIC USE OF GONADOTROPINS:
A. Gonadotropin preparations:
1. Urinary gonadotropin preparations (gonadotropins extracted from urine):
 Chorionic gonadotropin (PREGNYL) – from urine of pregnant women; mimics the action of LH
 Menotropins – from urine of postmenopausal women, contains FSH and LH (for i.m. injection)
 Urofollitropin – highly purified FSH (uFSH) – pure enough for s.c. injection
2. Recombinant gonadotropin preparations – (all pure, given s.c., may replace urinary preps):
 Recombinant FSH (rFSH) preparations (differ in their carbohydrate structures):
follitropin  (GONAL-F), follitropin  (PUREGON)
 Recombinant LH (LUVERIS)
 Recombinant hCG (OVIDREL)
B. Gonadotropin indications – treatment of infertility (female and male) and cryptorhidism:
1. Treatment of FEMALE infertility with FSH and hCG – fertilization in vivo and in vitro
a. Administration of FSH and hCG to assist in vivo fertilization:
Objective: to induce ovulation in anovulation (caused by hypogonadotropic hypogonadism or
polycystic ovary syndrome) or in normal ovulation (though the antiestrogen clomiphen is
attempted first), followed by an attempt for in vivo fertilization.
Regimen:  Administer FSH daily (75 IU) until cycle day 7 to initiate ovarian follicle development.
 Assess the number and sizes of developing follicles with transvaginal ultrasound.
One large follicle is desirable (If 3 or more large follicles develop, stop FSH and apply
barrier contraception to prevent multiple pregnancy.)
 Administer hCG (1 day after the last dose of FSH) to induce ovulation.
 Subsequent sexual intercourse may result in in vivo fertilization.
b. Administration of FSH and hCG to assist in vitro fertilization:
Objective: to induce ovulation in order to obtain several eggs for in vitro fertilization (IVF)
Regimen:  Administer FSH daily (225 IU) until cycle day 7 to initiate development of multiple
ovarian follicles. Also administer GnRH antagonist (e.g., ganirelix, cetrorelix) to
suppress LH secretion and to prevent premature ovulation.
 Administer hCG (1 day after the last dose of FSH) to induce ovulation.
 Before ovulation (it would occur in ~36 h), retrieve ova from the follicles transvaginally,
with an ultrasound-guided needle, piercing the vaginal wall to reach the ovaries.
 Fertilize the ova in vitro by incubating them with sperm (IVF) or
by injecting a spermium into an egg under microscope (ICSI).
 Transfer the fertilized eggs via a catheter into the uterus 3-5 days later.
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c. Unwanted effects of fertility treatment of women with FSH and hCG:
 Multiple pregnancy
 Ovarian hyperstimulation syndrome (OHSS):
Early OHSS develops before pregnancy testing, and late OHSS is seen in early pregnancy.
Mechanism:
hCG induces ovarian secretion of VEGF that  vascular permeability by
 claudin 5 expression in endothelial cells. (Claudin 5 is a cell adhesion
molecule in endothelial tight junctions.) Disruption of endothelial tight junctions
may cause fluid accumulation in the ovary, and in severe case even in the
peritoneal cavity, thorax, and pericardium.
Symptoms:
abdominal pain, bloating or distension; nausea and vomiting, diarrhea;
weight gain, dyspnoe, oliguria, enlarged ovaries.
Complications: ovarian torsion, ovarian rupture,
hypovolemia, electrolyte abnormalities, thromboembolization,
acute respiratory distress syndrome, hepatic dysfunction
Management: Withhold hCG if OHSS is suspected (symptoms, very high estrogen level).
Instead of hCG, induce ovulation with GnRH agonist (e.g. goserelin, leuprolide)
or recombinant LH. These have shorter T1/2 and are safer than hCG.
Apply supportive therapy.
2. Treatment of MALE infertility
Treatment of gonadotropin deficiency is performed in two phases:
(1) Administer androgens to induce sexual development.
(2) Administer gonadotropins (hCG  FSH  hCG) only when fertility is desired, as follows:
 Administer hCG (has LH-like effects), 3x weekly,
to activate Leydig cells for testosterone synthesis (monitor plasma testosterone),
then reduce hCG dose, and also
 Administer FSH, 3x weekly for 6 months,
to activate Sertoli cells to support spermiogenesis.
 Once spermiogenesis is fully established, hCG alone is usually sufficient to maintain it.
Adverse effects of fertility treatment of men with gonadotropins: gynecomastia.
Gynecomastia is probably caused by increased estrogen synthesis due to aromatase induction.
Aromatase is member of the cytochrome P450 superfamily (CYP19). Its function is to aromatize
androgens (androstendione, testosterone) to convert them into estrogens (estrone, estradiol).
Aromatase inhibitors (e.g., anastrazole, letrozole, aminoglutethimide) are used to treat breast
cancer. (Breast cancer is estrogen sensitive if the cancer cells express estrogen receptors.)
3. Treatment of cryptorhidism
 Cryptorhidism is the failure of one or both testes to descend into the scrotum.
Risks: - defective spermiogenesis  infertility
- development of germ cell tumors (germinoma), including dysgerminoma and seminoma
Therefore, testes should be repositioned ASAP, definitely before 2 years of age!
 Induction of testicular descent with hCG administration
Mechanism: hCG has LH-like effect and thus stimulates Leydig cells to produce testosterone.
Testosterone in turn promotes testicular descent.
Dose of hCG: 3000 IU/m2 i.m., every other day, 6 times
If testicular descent fails to occur, surgery (orchiopexy) should be performed!
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THYROID-STIMULATING HORMONE (TSH)
REGULATION OF TSH SECRETION:
Regulation of TSH secretion (see fig.)
  by:
TRH
- tripeptide of pyroGlu-Hys-Pro
- acts via TRH receptor on thyrotropes
 Gq  PLC  IP3  Ca2+
  by:
- negative feed back by T3 and T4
- somatostatin (via SST rec  Gi  AC)
- dopamine
MECHANISM OF TSH ACTION:
TSH acts on TSH receptors on thyroid cells ( Gq  PLC  IP3  Ca2+)
to increase synthesis and secretion of thyroid hormones (T3 and T4)
USES OF TRH AND TSH: none
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CORTICOTROPIN (ACTH)
THE SOURCE OF ACTH: POMC (pro-opiomelanocortin)
ACTH:
 is produced from POMC by prohormone
convertase 1 (PC1) together with other
substances (see figure)
 is a peptide of 39 amino acid
 certain residues are important in activity (6-10)
and receptor binding (15-18)
 its active derivative, Cosyntropin (CORTROSYN),
which contains the first 24 amino acid, is used
in the ACTH stimulation test.
REGULATION OF ACTH SECRETION:
Regulation of ACTH secretion (see figure)
  by: - CRH (via CRH rec on corticotropes  Gs  AC  cAMP  PKA)
- Stress (e.g., bleeding, surgery, trauma) and infection (IL-1, IL-2, IL-6, TNF)
  by: - negative feed back by cortisol
MECHANISM OF ACTH ACTION – melanocortin (MC) receptors
ACTH acts on melanocortin receptor-2 (MC2R) on cells of the adrenal cortex ( Gs  AC 
cAMP  PKA) to increase synthesis and secretion of cortical hormones (mainly cortisol, less so
aldosterone and DHEA, the precursor for androgens).
At high concentration, ACTH also stimulates melanocortin receptor-1 (MC1R), the receptor for
MSH on melanocytes. This explains the hyperpigmentation of patients with chronic
adrenocortical insufficiency (Addison’s disease), a condition with ACTH hypersecretion.
USES OF CRH AND ACTH: only diagnostic (CRH stimulation test, ACTH stimulation test)
13
B. POSTERIOR PITUITARY HORMONES
SON = Supraoptic nucleus
PVN = Paraventricular nucleus
AVP = arginine-vasopressin
OXY = oxytocin
Oxytocin and vasopressin (or ADH) are cyclic nonapeptides.
They are produced by hypothalamic neurons in supraoptic and paraventricular nuclei,
then are secreted by the nerve endings that terminate in the posterior pituitary.
A
H
O
HC
C
1
Tyr
X
Gln
Asn
2
3
4
5
C
H
Cys
6
S
Pro
Z
Gly
7
8
9
NH2
S
A
X
Z
RECEPTOR
Oxytocin
NH2
Ile
Leu
OT receptor
Vasopressin
NH2
Phe
Arg
V1 (in vsm), V2 (in rcd)
Desmopressin
H
Phe
D-Arg
V2
vsm = vascular smooth muscle; rcd = renal collecting duct
14
OXYTOCIN
REGULATION OF OXYTOCIN SECRETION:
 Stimulated by: - Sensory stimuli from the cervix, vagina, and breast (like prolactin)
- Hyperosmolality of the blood, i.e., dehydration (like ADH = vasopressin)
 Inhibited by:
- Relaxin  an ovarian polypeptide
- Ethanol  used for tocolysis
EFFECTS OF OXYTOCIN:
Two target organs: uterus and breast
1. Effects on uterus = uterotonic effect:
 induces rhythmic contraction of myometrium; frequency and force increasing with the a dose
 estrogens potentiate, progesterone inhibits its uterotonic effect
 sensitivity of uterus is variable: ~ immature uterus is insensitive
~ preterm uterus is highly sensitive, as the number of oxytocin
receptors in myometrium is increased.
2. Effects on the mammary gland:
 contracts the "myoepithelium" – smooth muscle surrounding the alveoli of the mammary gland
 milk ejection.
MECHANISM OF ACTION OF OXYTOCIN:
Oxytocin acts via G-protein-coupled receptors: Gq  PLC  IP3  Ca2+
THERAPEUTIC USE OF OXYTOCIN: given in i.v. infusion, because its T1/2 is only 3 min
Indications:
1. To induce labor: if pathologic pregnancy needs to be terminated
 Indications: premature rupture of the fetal membranes, isoimmunization,
uteroplacental insufficiency (e.g. in diabetes, pre-eclampsia, or eclampsia)
 To be verified before elective oxytocin infusion:
- The fetal lung is sufficiently mature (lecithin-sphingomyelin ratio in the amniotic fluid is >2)
- Lack of contraindications, e.g., abnormal fetal position, fetal distress, placental abnormality,
previous uterine surgery (risk for uterine rupture)
 Dose rate: starting rate: 1-2 mU/min, maximal rate: 40 mU/min
 Interrupt the infusion if: - contractions become too forceful and frequent
- the resting tone is elevated (would impair fetal oxygenation)
2. To augment labor: if labor is dysfunctional and the contractions are hypotonic (often during
epidural anesthesia)
3. To prevent postpartum uterine hemorrhage – administer a oxytocin at a large dose/dose rate:
 To be verified before oxytocin administration: the case is not multiple (e.g., twin) pregnancy
 Dosing regimens: - Bolus injection: 10 U i.m., or
- Infusion: ~ initially 200 mU/min until the uterus becomes contracted,
~ then 20 mU/min to maintain uterine contraction.
 Alternatives: - Ergot alkaloids: ergonovine, or methylergnovine (These induce tonic contraction,
therefore they should not be used to induce or augment labor!)
- Prostaglandin derivatives, e.g. misoprostol
4. To induce milk ejection:
 to relieve engorgement of the breast during lactation
 when breast feeding is inadequate
15
ADVERSE EFFECTS OF OXYTOCIN
 ADH-like effect: increased expression of AQP2 in distal convoluted tubules and collecting ducts
 increased renal water reabsorption
 increased risk for water intoxication
Do not infuse fluid over 3 L/day to an oxytocin-infused woman!
 Overstimulation of the uterus, which can cause complications, such as:
- Trauma to the mother or the fetus due to passage through an incompletely dilated cervix
- Uterine rupture
- Impaired fetal oxygenation due to decreased uterine circulation
VASOPRESSIN or ANTIDIURETIC HORMONE (ADH)
REGULATION OF VASOPRESSIN SECRETION:
ADH secretion is regulated primarily by plasma osmolality through the osmoreceptive neurons
which stimulate neurons in SON and PVN to secrete more vasopressin.
MECHANISMS OF ACTION OF VASOPRESSIN:
Vasopressin acts via two receptors (this explains why the hormone has two names):
 V1 receptors
- are coupled to Gq  PLC  IP3  Ca2+
- located: - on vascular smooth muscle  VASOCONSTRICTION ( vasopressin)
- on other cells, e.g. other smooth muscles (GI tract, uterus, bladder)
on platelets, hepatocytes, adipocytes, etc.
 V2 receptors
- are coupled to Gs  AC  cAMP  PKA
- located: on the principal cells of the renal collecting duct
 AQP2 INSERTION  WATER REABSORPTION ( ADH)
16
MECHANISM OF
THE SIGNAL
TRANSDUCTION
FROM
V1 RECEPTOR
Vascular or GI
smooth muscle
cell
(or liver cell,
or platelet)
MECHANISM OF
THE SIGNAL
TRANSDUCTION
FROM
V2 RECEPTOR
Principal cell
of the renal
collecting duct
17
VASOPRESSIN DEFICIENCY OR REFRACTORINESS AND THEIR TREATMENT
Vasopressin deficiency: CENTRAL diabetes insipidus (CDI)
 Caused by: decreased vasopressin secretion
- AQUIRED: hypothalamic injury (surgical or traumatic), disease (tumor, aneurism, ischemia)
- INHERITED: mutation of vasopressin pre-prohormone gene (usually autosomal dominant)
 Symptoms: polyuria (large volume of dilute urine)  polydipsia
 Diagnosis: desmopressin administration decreases urine flow and increases urine osmolality
 Treatment of central diabetes insipidus:
- Primary treatment: desmopressin, a selective V2 receptor agonist
- Adjuvant treatment: drugs that reduce urine volume in CDI by unknown mechanisms
~ Carbamazepine (a broad spectrum antiepileptic)
~ Chlorpropamid (a first generation oral antidiabetic)
~ Clofibrate (a first generation antihyperlipidemic)
Desmopressin: - Chemically: 1-deamino-8-D-arginine vasopressin (DDAVP)
- Is a selective V2 receptor agonist (unlike vasopressin)
- Its elimination is not too rapid (T1/2 ~60-120 min)
- Duration of effect is ~12 hrs; given 2x daily
- Administered ~ by injection (1-2 µg/day s.c.), or
~ by intranasal spray (10-40 µg/day), or
~ orally (100-200 µg/day; tablets); bioavailability is only ~1%!
- Adverse effect: water intoxication (plasma hyposmolality  brain edema)
Symptoms: lethargy, anorexia, nausea, vomiting,
muscle cramps, convulsions, coma, death
 Other uses of desmopressin:
- Hemorrhagic disorders, such as
~ Von Willebrand disease, type I (not other types): desmopressin  vW factor levels in plasma
~ Hemophilia A (not other types): desmopressin  VIII factor levels in the plasma. Apparently,
preformed vW and VIII factors are released from the endothel in response to desmopressin.
~ Other bleedings (cirrhosis- or heparin-induced)
Patients receiving desmopressin to maintain hemostasis should be advised
to reduce fluid intake in order to avoid water intoxication!
- Disorders in which induction of water retention is beneficial, such as
~ Enuresis nocturna: nasal spray is given at bedtime
~ Post-lumbar punction headache (to replenish lost CSF)
Vasopressin refractoriness: RENAL diabetes insipidus
 Cause: decreased antidiuretic effect of vasopressin
- AQUIRED: - Disorders: postobstructive renal failure, hypokalemia, hypercalcemia
- Drugs: lithium, clozapine, foscarnet; demeclocycline, methoxyflurane
- INHERITED (X-linked): mutation of V2-receptor gene
 Symptoms: polyuria (large volume of dilute urine)  polydipsia (like in CDI)
 Diagnosis: desmopressin fails to decrease urine flow and fails to increase urine osmolality
 Treatment of renal diabetes insipidus:
- Primary treatment: assurance of adequate water intake (desmopressin is ineffective)
- Adjuvant treatment: drugs that reduce urine volume in RDI by unknown mechanisms
~ Amiloride, in Li-induced RDI (blocks Li+ uptake via Na+ channels into the collecting duct cells)
~ Thiazide diuretics
~ Indomethacine (but not other NSAIDs)
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INAPPROPRIATELY LARGE VASOPRESSIN SECRETION
(causing antidiuretic effect and risk for brain edema) AND ITS TREATMENT
 Causes:
- DISORDERS, e.g., malignancies, pulmonary diseases, CNS injuries or diseases
- DRUGS: ~ Psychotropics (e.g., TCADs, fluoxetine, haloperidol)
~ Sulfonylureas (e.g., chloropropamide)
~ Antitumor drugs, e.g., vinca alkaloids (e.g., vincristin, vinblastin), ifosfamide
~ Others (e.g., clonidine, methyldopa, enalapril)
- EXTASY (methylenedioxy-metamphetamine, MDMA) – has caused fatal water intoxication
in youngsters taking Extasy and drinking much fluid in disco!
 Symptoms: - Oliguria with hyperosmotic urine
- Symptoms of water intoxication (plasma hyposmolality  brain edema):
lethargy, anorexia, nausea, vomiting, muscle cramps, convulsions, coma, death
 Diagnosis: desmopressin fails to further decrease urine flow and increase urine osmolality
(as vasopressin secreted excessively has produced a maximal antidiuretic effect)
 Treatment:
- Primary treatment: water restriction
- Adjuvant treatment:
~ Correction of plasma hyposmolality by i.v. administration of hypertonic saline or mannitol
~ Drugs that increase urine flow, e.g., loop diuretics
~ Drugs that decrease the effect of vasopressin, e.g. demeclocycline (a tetracycline antibiotic)
CLINICAL USES OF VASOPRESSIN – Objective: to stimulate V1 receptors
 Drug of choice: vasopressin (8-L-arginine vasopressin; PITRESSIN), V1 + V2 receptor agonist
 Indication:
- To promote intestinal motility by stimulating V1 receptors on of GI smooth muscle
in patients with postoperative ileus
- To induce vasoconstriction by stimulating V1 receptors in arteries in order:
(1) to reduce bleeding:
~ Bleeding due to pathologic conditions (esophageal varices, hemorrhagic gastritis,
hemorrhagic cystitis – may be induced by cyclophosphamide via forming acrolein.)
~ Bleeding after surgery (Cesarean section, uterine myoma resection, liver transplantation)
(2) to combat vasodilatory (or vasoregulatory) shock:
Vasopressin is given in combination with norepinephrine.
(3) to diminish elimination of local anesthetic from the site of application:
Vasopressin or ornipressin (8-ornithine-vasopressin) is selected
when epinephrine is contraindicated (e.g., in a patient with ventricular extrasystoles).
 Adverse effects:
Unwanted vasoconstriction, causing:
- Angina (can be counteracted by nitroglycerin)
- Gangrene in patients with peripheral artery disease
- Hypertension
19