Introduction: Subclinical hypothyroidism (SH) is associated with increased risk for atherosclerosis, mainly attributable to dyslipidemia, diastolic hypertension, altered coagulability and increased levels of inflammation markers. However, conflicting data exist regarding the effect of L-thyroxine substitution on these parameters.
The purpose of the present study was to quantify the effect of L-thyroxine therapy on lipid profile, coagulation markers, high-sensitivity C-reactive protein (hsCRP) and glucose homeostasis in patients with SH.
Description of methods/design: It was a comparative, prospective study conducted in the department of Endocrinology at a tertiary medical centre of northern Greece from November 2009 to November 2011. Patients with diabetes mellitus, cancer, renal, liver failure or receiving drugs affecting lipid metabolism or coagulation, were excluded.
The following parameters were measured before and 6 months after restoration of euthyroidism with increasing doses of L-thyroxine: anthropometric data, total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), triglycerides (TG), apolipoprotein B (apoB) and A1 (apoA1), lipoprotein (a) [Lp(a)], fasting plasma glucose and insulin, homeostasis model assessment-insulin resistance (HOMA-IR), hsCRP, antithrombin III (AT-III), protein C (PC), protein S (PS), fibrinogen and homocysteine.
Results: Thirty-two patients (30 women) aged 52.1±13.9 years with SH completed the study. Mean TSH levels at baseline were 6.79±2.58 mIU/ml. L-thyroxine and achievement of euthyroidism significantly reduced systolic blood pressure (BP) in patients with SH (from 135.2±18.5 to 129.7±15.8 mmHg, P=0.03) and diastolic BP only in those with baseline TSH levels >7 mIU/ml (from 79.5±9.8 to 72.1±7.3 mmHg, P=0.03).
No significant changes in body weight, waist or hip circumference, TC, LDL-C, HDL-C, TG, apoB, apoA1, Lp(a), glucose, insulin, HOMA-IR, hsCRP, AT-III, PC, PS, fibrinogen or homocysteine levels after restoration of euthyroidism.
Conclusions: Except for reduction in systolic and diastolic BP, thyroid substitution therapy does not affect lipidemic profile, systematic inflammation, glucose homeostasis or coagulation in patients with SH.
Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.
Funding: This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector
05 - 09 May 2012
European Society of Endocrinology