The relationships between thyroid hormones and thyroid-stimulating hormone with lipid profile in euthyroid men

Alteration in lipid profile is a common observation in patients with thyroid dysfunction, but the current knowledge on the relationship between lipids and thyroid hormone levels in euthyroid state is insufficient. The current study aimed to determine the association between thyroid hormones and thyroid-stimulating hormone (TSH) with lipid profile in a euthyroid male population.

A total of 708 Chinese and Malay men aged 20 years and above were recruited in this cross-sectional study. Their blood was collected for the determination of total cholesterol (TC), low density lipoprotein cholesterol (LDL-C), high density lipoprotein cholesterol (HDL-C), triglyceride (TG), free thyroxine (FT4), free triiodothyronine (FT3) and TSH levels. The association was analyzed using multiple regression and logistic regression models with adjustment for age, ethnicity, body mass index and FT4/FT3/TSH levels.

In multiple regression models, TSH was positively and significantly associated with TG (p<0.05). Free T4 was positively and significantly associated with TC, LDL-C and HDL-C (p<0.05). Free T3 was negatively and significantly associated with HDL-C (p<0.05). In binary logistic models, an increase in TSH was significantly associated with higher prevalence of elevated TG in the subjects (p<0.05), while an increase in FT4 was significantly associated with higher prevalence of elevated TC but a lower prevalence of subnormal HDL in the subjects (p<0.05). Free T3 was not associated with any lipid variables in the logistic regression (p>0.05).

In euthyroid Malaysian men, there are positive and significant relationships between TSH level and TG level, and between FT4 level and cholesterol levels.