Endocrine Abstracts

Long-term follow-up of differentiated thyroid cancer (DTC) patients requires yearly measurements of serum thyroglobulin (Tg) levels is endogenous (4 weeks off-thyroxin) or exogenous (human recombinant TSH injection) high TSH state. Subclinical hyperthyroidism is maintained in the patients throughout the rest of the year. We examined the endothelial function, hemostasis factors and metabolic parameters in short-term iatrogenic hypothyroidism (HO) and in subclinical hyperthyroidism (SH) in patients with DTC. In seventeen patients who had undergone total thyroidectomy and radioiodine ablation, blood pressure (RR), Tg, thyroid function, lipid parameters, homocystein, CRP, fibrinogen, von Willebrandt factor activity (vWF), flow-mediated vasodilatation (FMD) and nitroglycerin-mediated vasodilatation of the brachial artery in HO (TSH=89.82±29.36 mU/L) and in SH (TSH=0.24±0.11 mU/L) were measured. The study protocol has been approved by the institutional ethics committee. In HO the FMD was markedly lower than in SH (6.79±4.44 vs.14.37±8.33%, P<0.001), whereas the vasodilatation in response to nitroglycerine was not different between HO and SH (28.20±8.33 vs. 29.27±14.19%, ns). RR did not significantly differ in HO and SH (128.62±7.17/82.29±3.98 vs. 125.8±7.05/85.2±5.8 Hgmm, ns). Total cholesterol (7.34±1.23 vs. 4.75±/1.24 mmol/L, P<0.002), LDL-cholesterol (4.55±1.10 vs. 2.70±0.89 mmol/L, P<0.001) and homocystein (12.95±4.49 vs. 9.62±2.3 μmol/L, P<0.01) were significantly higher in HO than in SH. Triglyceride (1.79±1.12 vs. 1.03±0.73 mmol/L) and HDL-cholesterol (1.95±0.47 vs. 1.58±0.42 mmol/L) were similar in HO and SH. Fibrinogen (3.23±0.50 vs. 4.38±0.84 g/L, P<0.01), vWF activity (90.09±25.92 vs.130.62±29.97%, P<0.001) and CRP (4.12±4.67 vs. 5.32±5.15 mg/L, P<0.05) were lower in HO. In conclusion, FMD, fibrinogen and vWF activity was found to be lower in HO than in SH. Thyroxin normalizes the low FMD in HO patients.