Hemostasis in hyperthyroidism
FT4, and 0.35-5.50 μU/ml for TSH. Thyroid autoantibodies were
measured by an enzyme-linked immunosorbent assay (ELISA)
(Synelisa, Pharmacia, Germany). Antibody levels were consid-
ered negative when they were below 100 IU/ml. Serum total
cholesterol (TC) was measured using a cholesterol oxidase en-
zymatic method; triglycerides, were measured by a glycerol ox-
idase enzymatic method; high density lipoprotein cholesterol
(HDL-C), by a cholesterol oxidase enzymatic method in super-
natant after precipitation with phosphotungstic acid-MgCl2.
These routine analyses were carried out by autoanalyzer
(Technicon AXON). Low density lipoprotein cholesterol (LDL-C)
was calculated by the Friedewald’s formule. For coagulation and
fibrinolysis, a venous blood sample (9 vol) was collected into
Vacutainer tubes (Becton Dickinson, Mountain View, U.S.A.) con-
taining 0.129 mol/l trisodium citrate (1 vol). Platelet-poor plasma
was obtained by centrifugation 3500 ꢀ g at 10 C for 20 min.
Platelet count, mean platelet volume (MPV), prothrombin time
(PT), activated partial thromboplastin time (aPTT), fibrinogen,
antithrombin III (AT III), factors V, VII, VIII, IX and X measure-
ments were performed immediately. Aliquots of plasma were
transferred into plastic tubes without delay and frozen at -80 C
until assays for determination of vWF, protein C, protein S, t-
PA, and PAI-1. Platelet count and MPV was measured with au-
tomatic cell counter (Coulter Micro Diff II). PT and aPTT were
determined with coagulometer, using, commercial kits of
Diagnostica Stago. Fibrinogen was determined using a neph-
elometric assay by commercial kits for fibrinogen (Cat No.OSCA
09, Dade Behring Marburg GmbH, Germany). Factors V, VII, VI-
II, IX and X activities were measured with coagulometer
(Diagnostica Stago) using commercial kits of Diagnostica Stago.
AT III assay was performed with spectrophotometric method
(Behring turbitimer, Turbiquant, AT III, Dade Behring).Normal
ranges are 200-400 mg/dl for fibrinogen, 50-150% for Factors V,
FVII, FVIII, FIX and FX. Protein C and Protein S activity assays
were performed with ELISA method using commercial kits of
Biopool International. vWF activity was determined by ELISA
method using commercial kits of Imtec Immundiagnostica
Gmbh. t-PA and PAI-1 assays were performed with ELISA using
commercial kits of American Diagnostica. According to the man-
ufacturer, normal ranges are 22-39 mg/dl for AT III, 70-150% for
vWF, 72-160% for protein C activity, 60-150% for protein S ac-
tivity, 1-20 ng/ml for t-PA Ag, and 20-44 ng/ml for PAI-1 Ag.
Statistical analysis was performed by Student’s t test, Mann-
Whitney U test, and multiple regression analysis. Results are pre-
sented as mean SD. The calculations were performed using SPSS
for Windows (SPSS, Inc., Chicago, U.S.A.).
nolytic activity (9, 10). Finally, strong indications exist
that hyperthyroidism influences endothelial function.
Levels of soluble vascular adhesion molecules and
thrombomodulin are increased in hyperthyroidism,
regardless of of its etiology (11-13).
Furthermore, the administration of thyroid hormone
to healthy volunteers significantly increases plasma
levels of von Willebrand Factor (vWF), a change sim-
ilar to that found in hyperthyroid patients (7). In-
creased vWF activity has been reported in hyper-
thyroid patients (6, 11). In contrast, vWF in circulating
blood originates mainly from the endothelium, and
high plasma levels are widely accepted as an im-
portant indicator of endothelial dysfunction (14). Until
recently, changes in other endothelium-derived pro-
teins, such as tissue plasminogen activator (t-PA) and
plasminogen activator inhibitor 1 (PAI-1), in hyper-
thyroid patients had not been reported. However,
literature data on the influence of thyroid function
on coagulation/fibrinolysis are ambiguous and often
contradictory. This may be related to the use of old-
er methodology, to the inclusion of patients with a
different etiology of hyperthyroidism or to the fact
that a highly variable relation exists between thyroid
dysfunction and the coagulation process.
The main purpose of this study was to investigate
the markers of endogenous coagulation/fibrinoly-
sis and of vascular endothelial cell function, and to
evaluate the relationships between serum lipid pro-
file, thyroid hormones and hemostatic parameters
in hyperthyroid patients.
PATIENTS AND METHODS
The study was carried out at the Karadeniz Technical University
Medical Faculty, Department of Internal Medicine. Forty-one
untreated hyperthyroid patients [12 men (M), 29 women (W);
aged 44.5 15.2 yr] were included; 20 patients with Graves’ dis-
ease, and 21 patients with toxic nodular goiter (16 multinodular
and 5 with toxic adenoma). Each patient was clinically and bio-
chemically hyperthyroid, defined as having increased serum thy-
roid hormone levels, a suppressed TSH concentration (<0.1
μU/ml). The diagnosis of Graves’ disease was based on the ad-
ditional presence of a smooth goiter, thyroid autoantibodies
[anti-TG, anti-thyroid peroxidase (anti-TPO) and anti-TSH re-
ceptor], or specific eye signs. Patients were taking neither drugs
nor had diseases (e.g. diabetes mellitus, collagen disease, liver
cirrhosis, atrial fibrillation, or renal disease) known to affect blood
coagulation or fibrinolysis at the time of the study. Twenty heal-
thy age- and sex-matched subjects (6 M, 14 W; aged 46 14.9 yr)
were used as controls.
RESULTS
Table 1 summarizes the clinical characteristics and
clinical data in patients with hyperthyroidism and
control subjects. Compared with the control sub-
jects, AT III, fibrinogen, F IX, vWF and PAI-1 were
significantly increased in hyperthyroid patients
(p<0.01, p<0.05, p<0.0001, p<0.05 and p<0.0001;
respectively), whereas F X and t-PA were decreased
(p<0.05). For protein C, protein S and the other co-
agulation factors’ activities in hyperthyroid patients
were not different from the controls.
Blood was collected in the morning 08:00-09:00 h after an
overnight fast. Serum total (TT3) and FT3, total and free thyrox-
ine (TT4 and FT4), and TSH concentrations were measured by
an automated chemiluminescence system (Bayer Corporation,
Tarrytown, U.S.A.). Normal ranges are 0.6-1.81 ng/ml for TT3,
4.5-10.9 μg/dl for TT4, 2.3-4.2 pg/ml for FT3, 0.89-1.76 ng/dl for
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