Interesting that TSH and FT4 show no significant association with vitamin D, but FT3 does. Certainly shows yet another way in which TSH is not perfectly correlated to thyroid hormone levels.
LURIC: Vitamin D levels correlate with increased FT3 levels
May 17, 2015
NASHVILLE, Tenn. — A significant association was found between serum 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D and increased free triiodothyronine levels, according to study findings presented here.
However, no significant association was found between vitamin D levels and thyroid-stimulating hormone (TSH) or free thryoxine (FT4), according to researchers.
“Accumulating evidence suggests a complex interplay between thyroid hormone status and vitamin D,” the researchers wrote. “Previous studies showed that thyroid hormone inhibits 25-(OH)D 1-alpha hydroxylase and that vitamin D suppresses TSH secretion and exerts direct effects on thyroid cells such as [in the] inhibition of iodine uptake. Clinical data on direct effects are, however, sparse and partially controversial.”
Anette Merke, MD, of the Thyroid Center Bergstrasse in Germany, and colleagues evaluated 2,804 participants (mean age 62.8 years; 30% women) from the Ludwigshafen Risk and Cardiovascular Health (LURIC) Study to determine if serum 25-(OH)D and 1,25-dihydroxyvitamin D (1,25-(OH)D) is linked to TSH, FT4 and free triiodothyronine (FT3) levels. All patients were referred for angiography.
Linear regression analysis was performed for TSH, FT4 and FT3; adjustments were made for age, sex, BMI and active smoking status.
Although no significant association was found between vitamin D levels and TSH or FT4, a significant association was found for serum 25-(OH)D and FT3 (P = .043) and serum 1,25-(OH)D and FT3 (P < .001).
“The mechanisms by which thyroid hormones influence vitamin D metabolism is still unknown,” the researchers wrote. “Thyroid hormones, ie, FT3, exert their actions by binding to thyroid hormone receptors, which belong to the nuclear receptor superfamily including the vitamin D receptors; polymorphisms in the [vitamin D receptor] gene have been associated with autoimmune thyroid disease. The reason for the close relationship between FT3 and vitamin D remains speculative. To our best knowledge this is the first [study] to report a correlation between FT3 and vitamin D levels.”
According to the researchers, more studies are needed to fully comprehend the pathophysiological systems of the association between metabolites. – by Amber Cox
Merke A, et al. Abstract 1085T. Presented at: AACE 24th Annual Scientific & Clinical Congress; May 13-17, 2015; Nashville, Tenn.
Disclosure: The researchers report no relevant financial disclosures.
Ludwigshafen Risk and Cardiovascular Health (LURIC) Study