High Fibrinogen and Plasminogen Activator Inhibitor Activity in

434
High Fibrinogen and Plasminogen Activator
Inhibitor Activity in Growth
Hormone-Deficient Adults
Jan-Ove Johansson, Kerstin Landin, Lilian Tengborn, Thord Rosen, Bengt-Ake Bengtsson
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Abstract Hypopituitary patients on routine replacement
therapy except growth hormone (GH) have an increased risk of
death from cardiovascular diseases compared with healthy subjects. Untreated GH deficiency might explain the premature
death from vascular disease. Plasminogen activator inhibitor
(PAI-1) activity, fibrinogen, insulin, blood lipid, and blood pressure levels were studied in 20 GH-deficient adults (10 men, 10
women) 50±ll years old with routine hormone replacement
therapy (except GH) and compared with 20 healthy control
subjects matched for sex, age, and body mass index. GH-deficient
subjects had a higher waist-to-hip circumference ratio (P<.001),
serum triglycerides (/><.O2), PAI-1 activity (13.2±10.6 versus
6.8+4.8 U/mL [P<.05]), and fibrinogen (3.2±0.7 versus 2.4±0.6
g/L [P<.001]) and lower blood glucose (P<.05) compared with
control subjects. Blood pressure, insulin, and cholesterol levels
were similar. The aberrations found in this study might contribute to an increased atherothrombotic propensity and play a role
in the pathogenesis of cardiovascular disease. {Arteriosder
Thwmb. 1994;14:434-437.)
Key Words • growth hormone deficiency • plasminogen
activator inhibitor-1 • fibrinogen • triglycerides • insulin
• glucose • waist to hip ratio
H
these patients and compared the results with those from
healthy subjects who were matched for sex, age, and
body mass index (BMI).
ypopituitary patients on routine replacement
therapy except growth hormone (GH) have an
increased risk of death from cardiovascular
diseases compared with healthy subjects.1 The cause of
death from vascular disorders is unclear, although untreated GH deficiency may play an important role.
Recently, hypopituitary patients with untreated GH
deficiency were found to have more atheromatous
plaques in the carotid and femoral arteries compared
with healthy age- and weight-matched control subjects.2
This observation gives further support for a possible
association between hypopituitarism and premature
atherosclerosis.
The importance of GH for the regulation of plasma
lipids is not yet fully documented, and the results are
somewhat conflicting. However, data suggest that GHdeficient adults have an increased low-density lipoprotein (LDL) to high-density lipoprotein (HDL) cholesterol ratio and that treatment with recombinant human
GH reduces LDL and increases HDL cholesterol.3
Furthermore, body fat is increased in GH-deficient
patients, which might raise the risk of cardiovascular
diseases/ Obesity, and in particular abdominal fat
distribution, is associated with increased concentrations
of fibrinogen and plasminogen activator inhibitor
(PAI-1) activity.5-6 Fibrinogen has been shown to be an
independent risk factor for stroke as well as myocardial
infarction,7 and PAI-1 activity has been associated with
increased risk for recurrent myocardial infarction.8
To further elucidate the "risk profile" for cardiovascular disorders in adults with GH deficiency, we studied
fibrinogen concentration as well as PAI-1 activity in
Received April 20, 1993; revision accepted December 14, 1993.
From the Department of Medicine, Sahlgrenska Hospital, University of GOteborg, G6teborg, Sweden.
Correspondence to Kerstin Landin, MD, PhD, Department of
Medicine, Sahlgrenska Hospital, S-413 45 Goteborg, Sweden.
Methods
Subjects
Twenty patients (10 women and 10 men) 30 to 65 years old
who had been investigated previously as inpatients at the
Division of Endocrinology because of adult-onset pituitary
insufficiency were asked to participate in the study. All patients were treated with adequate replacement therapy of
glucocorticoids (cortisone acetate 25 to 50 mg/d), thyroid
hormones (L-thyroxine 0.10 to 0.15 mg/d), and sex hormones.
GH deficiency was defined as a maximum GH response of <5
mU/L after insulin-induced hypoglycemia (0.1 IU/kg body
weight [Actrapid Human, Novo, Copenhagen, Denmark]).
None of the patients had previously been treated with GH.
Mean duration of known hypopituitarism was 12±10 years.
The characteristics of the 20 patients in the study are shown in
Tables 1 and 2. One patient was treated with a calcium
blocker, 1 with a /J-blocker, and 1 with an angiotensinconverting enzyme inhibitor because of hypertension.
The 20 healthy control subjects were recruited by means of
an advertisement in the local newspaper. The criteria for being
healthy, besides subjective well-being, were a history of no
hospital visits, no diabetes or hypertension, and no medical
treatment for any disease during the previous 2 years. Of 255
respondents in the age group 40 to 60 years, 207 fulfilled the
criteria for healthy control subjects. Ten men and 10 women
were groupwise anthropometrically matched for age, sex, and
BMI. One patient and 3 control subjects were smokers.
The patients received both written and verbal information
about the study, and their informed consent was obtained. The
study was approved by the Ethics Committee of the Medical
Faculty at the University of Goteborg.
Anthropometry
Body height and weight were measured in the morning with
the subjects wearing only underclothes. Waist circumference
was measured with a soft tape at the level of the umbilicus in
Johansson et al
TABLE 1. Age and Anthropometric Data In 20 Growth
Hormone-Deficient Patients and Healthy Control Subjects
Control
Subjects
(n=2O)
Patients
(n=20)
Variable
Age, y
Fibrinogen
9/L
p=O.0O1
52(43-57)
NS
10/10
10/10
NS
Height, cm
173(157-195)
174(154-190)
NS
Weight, kg
80(57-109)
79 (61-100)
NS
Body mass Index,
kg/m2
26.4 (225-32.2)
26.1 (21.4-35.4)
NS
3
2
Values are means, with ranges in parentheses.
the standing position. Hip circumference was measured over
the widest part of the hip region, and the waist-to-hip circumference ratio (WHR) was calculated.
Biochemical Assays
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Venous blood samples were taken after an overnight fast for
the determination of blood glucose by a glucose oxidase
method (Kabi, Stockholm, Sweden), and plasma insulin levels
were analyzed by a radioimmunoassay technique using kits
from Pharmacia (Uppsala, Sweden). Cholesterol concentration was determined according to the method described by
Allain et al.9 Triglyceride concentration was determined with a
fully enzymatic method (Boehringer, Mannheim, Germany)
according to Fossati and Prencipe.10 Blood samples were
drawn in precooled 5-mL Vacutainer tubes containing 0.5 mL
of 0.13 mol/L trisodium citrate (Becton Dickinson, Meylan,
France) and used for determination of fibrinogen according to
a syneresis method11 and PAI-1 activity with the reagent from
Spectrolyse, Biopool, Umea, Sweden. All tubes were immediately centrifuged at 4°C and 2000g for 20 minutes. The
coefficient of variation was 10% for PAI-1 activity, equal to 6
U/mL, and 6% for PAI-1 activity, equal to 44 U/mL. GH was
determined by an immunoradiometric assay according to the
manufacturer's protocol (Pharmacia).
Blood Pressure Measurements
Blood pressure was calculated to the nearest 5 mm Hg as the
mean of three measurements on the right arm after 10 minutes
in the supine position. Diastolic pressure was measured as
Korotkoff phase V. A mercury sphygmomanometer was used.
TABLE 2.
435
P
50(30-65)
Sex, M/F
Flbrinolysis in Growth Hormone Deficiency
Characteristics of the 20 Patients (10 Men, 10
Women) With Growth Hormone Deficiency
Men
Women
Chromophobe adenoma
7
•8"
Diagnosis
Prolactinoma
2
0
Craniopharyngloma
a
£
Pituitary cyst
0
1
Sheehan's syndrome
0
1
Idtopathic hypopituitarism
i
0
Replacement treatment
CortJcosteroid
3
a
Thyroxlne
e
10
Gonadal steroids
8
s
Desmopressin
1
3
i
GH Controls
deficiency
n=1O n=1O
GH Control*
deficiency
n=1O n=1O
Men
Women
Bar graph showing fibrinogen concentrations in growth hormone
(GH)-deficient adults and healthy control subjects. Values are
mean±SD.
A cuff size corresponding to the circumference of the right arm
was chosen.12
Statistical Analysis
Mean values, standard deviations, and linear regression
were calculated by conventional methods. Differences between
groups were tested with the exact permutation test. Values of
P<.05 (two-sided tests) were considered to be significant.
Results
Although patients and control subjects were matched
for BMI (Table 1), WHR was higher in the patients
than in the control subjects calculated from both sexes
together (0.97±0.03 versus 0.87±0.09, P<.001). WHR
was similar in male and female patients, but there was a
difference between healthy men and women (,P<.001).
Female but not male patients and control subjects
differed in WHR (/><.001) (Tables 3 and 4).
Serum triglyceride concentration was higher and
blood glucose lower in all patients together as well as in
GH-deficient men compared with their respective control subjects (Tables 3 and 4). Fasting plasma insulin,
cholesterol, and blood pressure levels were similar in
patients and control subjects, including both sexes (Table 3). However, cholesterol was higher in GH-deficient
men and systolic blood pressure higher in GH-deficient
women compared with their sex-matched control subjects (Table 4).
Fibrinogen concentration was higher in patients than
in control subjects (P<.001) irrespective of sex (see
Tables 3 and 4 and the Figure). Also, PAI-1 activity was
higher among the patients, including both sexes, than in
the control subjects (P<.05) (Table 3), whereas the
differences were less pronounced when men and women
were studied separately (Table 4).
PAI-1 activity among the patients correlated with the
triglyceride concentration (r=.A0, P<.05), the insulin
concentration (r=.51, /><.0Ol), and the blood glucose
level (r=.51, P<.00l). Neither PAI-1 nor fibrinogen
concentration correlated with cholesterol or insulin-like
growth factor-1 levels, respectively.
Discussion
The results of the present study add a new dimension
to the risk factor profile for adult patients with GH
436
Arteriosclerosis and Thrombosis
Vol 14, No 3 March 1994
TABLE 3. Metabolic Data, Fibrinogen, Plasmlnogen Activator lnhlbitor-1 Activity, Blood
Pressure, and Waist/Hip Circumference Ratio In Adult Patients With Growth Hormone
Deficiency and Healthy Control Subjects
Variable
Patients
(n=20)
Control Subjects
(n=20)
P
Fasting blood glucose, mmol/L
4.0+0.5
4.4±0.7
.042
Fasting plasma insulin, mU/L
7±2
8±2
.839
6.3 + 1.2
5.8+1.2
.266
Triglycerides, mmol/L
1.5±0.5
1.1 ±0.5
.019
Fibrinogen, g/L
3.2±0.7
2.4±0.6
.0001
PAI-1 activity, U/mL
13.2±10.6
6.8±4.3
.013
Systolic blood pressure, mm Hg
136±22
130±13
.319
Diastolic blood pressure, mm Hg
79±7
81 ±7
.360
0.87±0.09
.0001
Cholesterol, mmol/L
Waist/hip circumference ratio
0.97±0.03
PAI-1 indicates plasminogen activator inhibitor-1. Values are mean±SD.
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deficiency. Elevated fibrinogen and PAI-1 activity together with increased WHR and triglyceride concentrations link thrombogenesis with atherogenesis and might
explain the increased risk for atherothrombotic
complications.
In the study by Markussis et al2 showing increased
incidence of atherosclerotic plaques in the arterial
vessel walls among patients with hypopituitarism including GH deficiency, the patient group had higher cholesterol levels than the control group, but in contrast to our
findings, the fibrinogen did not differ between patients
and weight-matched control subjects. In that study,
however, the fibrinogen levels were quite high, >3 g/L
for the control subjects at an age and BMI similar to
those of the subjects of the present study. In our
experience, such high fibrinogen levels were found only
in grossly obese women with abdominal fat distribution
among different patient categories studied at our coagulation unit.6
Previous population-based studies have shown that
fibrinogen concentration is an independent risk factor
for cardiovascular disease and at least as important a
factor as blood pressure and blood lipids.7 A strong
association between smoking habits and fibrinogen con-
centration has also been observed.7 However, the high
fibrinogen concentration observed in our study cannot
be explained by smoking habits, since only one of our
patients was a current smoker.
Obesity has been associated with higher PAI-1 activity.56 Although patients and control subjects were
matched for BMI, we observed higher PAI-1 activity
among our patients than in control subjects, suggesting
that other factors besides obesity per se are important.
In normal obese subjects, higher fibrinogen and PAI-1
activity have been observed in those with the highest
WHR, indicating an abdominal fat distribution.6 Possibly, the high fibrinogen and PAI-1 activity observed in
the patients of the present study might be linked to the
markedly higher WHR in our patients than in the
control subjects. A markedly high WHR, 0.97±0.02, was
found in GH-deficient women in this study. The prevalence of a WHR 20.80 in healthy women with BMI
similar to that in the present women was only 9% among
the 145 women at the screening.13 However, WHR was
not significantly different between GH-deficient men
and control subjects, among whom the fibrinogen concentrations were greatly divergent, as seen in Table 4.
High triglycerides might contribute to the elevated
TABLE 4. Metabolic Data, Fibrinogen, Plasmlnogen Activator lnhlbltor-1 Activity, Systolic and Diastolic Blood
Pressures, and Walst/HIp Circumference Ratio In Adult Patients With Growth Hormone Deficiency and Healthy
Control Subjects
Men
Women
Variable
Patients
Control Subjects
P
Patients
Control Subjects
P
Glucose, mmol/L
4.1 ±0.5
4.8±0.06
.010
3.8±0.4
3.9±0.5
.707
7±2
6±2
.147
7±3
9±2
.177
Cholesterol, mmol/L
6.7±0.7
5.0±0.6
.0001
5.9±1.4
6.7±1.1
.154
Triglycerides, mmol/L
1.8±0.5
1.0±0.5
.004
1.3+0.4
1.3±0.4
.959
Insulin, mU/L
3.0±0.4
2.2±0.5
.001
3.5±0.8
2.5±0.6
.008
PAI-1 activity, U/mL
15.4±13.5
8.0+2.7
.135
11.1+6.6
5.7±5.3
.063
Systolic blood pressure, mm Hg
130±21
138±12
.315
142±21
123+9
.018
Diastolic blood pressure, mm Hg
80±8
86+5
.053
78±6
76±5
.483
0.97+0.04
0.93±0.05
.062
0.97±0.02
Fibrinogen, g/L
Waist/hip circumference ratio
PAI-1 indicates plasminogen activator inhibitor-1. Values are mean±SD. n = 1 0 l n each group.
0.81 ±0.07
.0001
Johansson et al Fibrinolysis in Growth Hormone Deficiency
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PAI-1 activity in GH-deficient men. As has been observed previously in lean men and obese women, we
observed a relation with PAI-1 activity and insulin,
glucose, and triglyceride levels.614
Previous studies have shown that adipose tissue is
markedly increased in GH deficiency.4 The increase is
mainly in abdominal depots, which is supported by our
own and others15 observations of high WHR. In fact,
such high WHR as observed among our patients was not
seen even in grossly obese women, even if BMI was 36
kg/m2.13 Treatment with recombinant human GH results in a decrease of total adipose tissue as well as a
redistribution of adipose tissue from visceral to subcutaneous depots. 1517 These changes have been associated with GH-induced reductions of the antilipolytic
effect of insulin, which is markedly altered in different
adipose tissue regions.18
Low blood glucose level was found among our patients, especially in men; similar observations have been
made earlier19 and might be a result of a decreased
hepatic glucose production. Plasma insulin concentrations were similar to those of control subjects and within
the normal range.
GH deficiency might well explain the findings in the
present study of increased WHR, increased concentrations of triglycerides and fibrinogen, and increased
PAI-1 activity. We have shown previously that GH
deficiency in adults is associated with a higher prevalence of hypertension, increased levels of triglycerides,
and lower HDL cholesterol concentrations.20 All are
factors that fit into the so-called metabolic or insulinresistance syndrome,21 which has been extended by
inclusion of elevations of fibrinogen and PAI-1 activity
independent of obesity.14
We cannot exclude the possibility that the replacement therapy given to the patients may have affected
the variables studied. It is unlikely, however, that physiological replacement therapy induces metabolic effects
of the magnitude detected in this study. Furthermore,
no patients with replacement therapy of either type had
extreme divergence from the mean values in any of the
variables studied.
The four subjects with hypertension had somewhat
higher PAI-1 activity and fibrinogen levels, which is in
accordance with previous results.14 Even if these hypertensive subjects were excluded, the mean values of
PAI-1 and fibrinogen still differed from those of the
control subjects. These observations add further similarities to the metabolic syndrome.
In conclusion, adults with GH deficiency have high
fibrinogen and PAI-1 activity levels. These aberrations
might contribute to an increased risk for atherothrombotic events and play a role in the pathogenesis of
cardiovascular diseases that are found in patients with
hypopituitarism.
Acknowledgments
This study was supported by grants from the Goteborg
Medical Society. We thank Ingrid Hansson, Anne Rosen,
Lena Wiren, Kaisa Torstensson, and the staff at the coagulation unit for excellent technical assistance.
437
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High fibrinogen and plasminogen activator inhibitor activity in growth hormone-deficient
adults.
J O Johansson, K Landin, L Tengborn, T Rosén and B A Bengtsson
Arterioscler Thromb Vasc Biol. 1994;14:434-437
doi: 10.1161/01.ATV.14.3.434
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