Possible Interaction: Thyroxine and Vitamin D

“ D3 terminates thyroid hormone action by inactivation of both T4 and T3 molecules.”

“In contrast, D3 catalyzes the inactivation of both T4 and T3 via inner-ring deiodination.”

“Furthermore, 25-hydroxyvitamin D was negatively correlated with the free thyroxine level (r = −0.1286, p = .0323) as well as the free triiodothyronine level (r = 0.1247, p = .0380).”

“Linear regression analysis showed a significant association of 25-hydroxyvitamin D concentrations with HDL and T4 after adjustments based on the sex.”

“Serum levels of 25-hydroxyvitamin D had a negative significant correlation with triiodothyronine (T3) and T4 , and a positive correlation with HDL.”

“The concentrations of 250HD3 and of 24,25-dihydroxycholecalciferol (24,25(OH)2D3) were significantly higher and those of cholecalciferol and of 1,25-dihydroxycholecalciferol (1,25(OH)2D3) were significantly lower in the plasma and tissues of animals treated with thyroxine than in controls.”

“ D3 inactivates thyroxine ( T4 ) and T3 by 5-deiodination, and the gene for this enzyme, Dio3, lies in the imprinted domain on human chromosome 14q32/distal mouse chromosome 12.”

“Binding of T4 and D3 are not competitive, indicating separate binding sites for the two ligands; in fact, T4 tends to enhance the affinity and the capacity for D3.”

“Tests staged on normal and hypophysectomized rats demonstrated thyroxin to potentiate the general toxic effect of ergocalciferol , with final death of the animals.”

“Although the combination of vitamin A or thyroxine with vitamin D3 reduces the tendency of vitamin D3 to cause metastatic calcification the combinations may not be so effective in preventing milk fever.”

“This syndrome results from the aberrant uncontrolled expression of D3 that can induce a severe form of hypothyroidism by inactivating T4 and T3 in defined tumor tissue.”