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Effects of Thyrotropin on Peripheral Thyroid Hormone Metabolism and Serum Lipids.

Effects of Thyrotropin on Peripheral Thyroid Hormone Metabolism and Serum Lipids.
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Beukhof CM, Massolt ET, Visser TJ, Korevaar TIM, Medici M, de Herder WW, Roeters van Lennep JE, Mulder MT, de Rijke YB, Reiners C, Verburg FA, Peeters RP,


Beukhof CM, Massolt ET, Visser TJ, Korevaar TIM, Medici M, de Herder WW, Roeters van Lennep JE, Mulder MT, de Rijke YB, Reiners C, Verburg FA, Peeters RP, (click to view)

Beukhof CM, Massolt ET, Visser TJ, Korevaar TIM, Medici M, de Herder WW, Roeters van Lennep JE, Mulder MT, de Rijke YB, Reiners C, Verburg FA, Peeters RP,

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Thyroid : official journal of the American Thyroid Association 2018 02 01() doi 10.1089/thy.2017.0330

Abstract
BACKGROUND
Subclinical hypothyroidism is associated with dyslipidemia and atherosclerosis. Whether these effects are in part mediated via direct effects of thyrotropin (TSH) on peripheral thyroid hormone (TH) metabolism and/or concentrations of serum lipids is not clear.

OBJECTIVE
This study examined whether TSH has direct effects on peripheral TH metabolism and serum lipids.

METHODS
Eighty-two patients with differentiated thyroid cancer were retrospectively analyzed. All patients had undergone total thyroidectomy and 131I remnant ablation. During follow-up, two successive injections of recombinant human TSH (rhTSH) were administered to 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, low-density lipoprotein cholesterol, apolipoprotein B, lipoprotein(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 apolipoprotein B increased from 0.90 to 0.92 g/L (p = 0.03), lipoprotein(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 high-density lipoprotein cholesterol decreased from 0.98 to 0.81 mmol/L (p < 0.001). Multiple regression analysis showed that the changes in lipids were most closely associated with 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.

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