Effects of thyroid stimulating hormone on peripheral thyroid hormone metabolism and serum lipids.

Effects of thyroid stimulating hormone on peripheral thyroid hormone metabolism and serum lipids.

Thyroid. 2018 Jan 09;:

Authors: Beukhof CM, Massolt ET, Visser TJ, Korevaar T, Medici M, de Herder WW, Roeters van Lennep J, Mulder M, de Rijke YB, Reiners C, Verburg FA, Peeters R

Abstract
BACKGROUND: Subclinical hypothyroidism is associated with dyslipidemia and atherosclerosis. Whether part of these effects are mediated via direct effects of TSH on peripheral TH metabolism and/or concentrations of serum lipids is not clear.
OBJECTIVE: To examine whether thyroid stimulating hormone (TSH) has direct effects on peripheral thyroid hormone (TH) metabolism and serum lipids.
METHODS: We retrospectively analyzed 82 patients with differentiated thyroid cancer. All patients had undergone total thyroidectomy and 131I remnant ablation. During follow-up, two successive injections of recombinant human TSH (rhTSH) were administered in patients on a stable dose of levothyroxine. In all patients, TSH, thyroxine (T4), free T4 (FT4), triiodothyronine (T3), reverse T3 (rT3), total cholesterol, high density lipoprotein cholesterol (HDL-C), low density lipoprotein cholesterol (LDL-C), apolipoprotein B (apoB), lipoprotein(a) [Lp(a)] and triglyceride levels were measured immediately before the first, and approximately 72 hours after the second injection of rhTSH.
RESULTS: After rhTSH stimulation, T3 values decreased (from 1.91 to 1.81 nmol/l, p<0.001). T4, FT4 and rT3 did not change. After rhTSH, median apoB increased from 0.90 to 0.92 g/l (p=0.03), Lp(a) from 0.21 to 0.24 g/l (p<0.001) and triglycerides from 1.98 to 2.50 mmol/l (p<0.001). Serum HDL-C decreased from 0.98 to 0.81 mmol/l (p<0.001). Multiple regression analysis showed that the changes in lipids could be attributed to the decrease in T3 levels.
CONCLUSIONS: TSH has direct effects on peripheral TH metabolism by decreasing T3 levels in levothyroxine-treated thyroidectomized patients. This decrease in T3 levels is accompanied by unfavorable changes in serum lipids.

PMID: 29316865 [PubMed - as supplied by publisher]

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