Possible Interaction: Melatonin and Triiodothyronine

“ Melatonin implantation resulted in an increase in IGF-1 concentrations and lesser estradiol (E2) and triiodothyronine (T3) concentrations.”

“Melatonin is a hormone known to modulate the estrous cycle and pregnancy, and studies show that the exogenous application of melatonin increased T4 levels in female rats and controlled the decrease in T3 serum levels, reverting the sigs of hypothyroidism.”

“An inhibition of triiodothyronine and thyroxine was detected, as a result of melatonin administration.”

“Treatment of rats daily with T3 (8 μg/100 g BW) for 15 days resulted in an increase in heart weight to body weight ratio, which was ameliorated by antioxidants, melatonin (2 mg/100 g BW) or vitamin E (4 mg/100 g BW).”

“Exogenous melatonin administration caused delays in the acrophases of T3 , T4 and melatonin rhythm itself; whereas advances in the acrophases of TSH were observed, thus indicating chronic administration of melatonin could alter the characteristics of endocrine rhythms.”

“ Melatonin decreased T4 secretion during the first 30 hr, but … during the last 24 hr of culture, suppressed 3,5,3'-triidothyronine (T3) secretion for 12 hr, and then raised T3 output into the media above … control for the remainder of the culture period, increasing the T3:T4 ratio.”

“Exogenous melatonin has the suppressive effect of diurnal secretion of T3 , T4 and testosterone in pinealectomized rats but stimulates the rhythmical corticosterone secretion.”

“Furthermore, ML-23 antagonized the effects of melatonin on plasma thyroxine levels and significantly increased plasma triiodothyronine concentrations and the free triiodothyronine index when used in combination with melatonin.”

“In dark, T3 decreased melatonin levels in the pineals of either age, but was without significant effect on levels in the medium.”

“In light, T3 increased melatonin levels in pineal and medium of cultures from either young or maturing animals.”

“Since it is known from other work that 14‐day‐old rat pineal glands do not yet have a complete sympathetic innervation system, it is here doubly evident that T3 can modulate directly pineal synthesis and release of melatonin , and may not depend upon a mature sympathetic innervation.”

“The higher dose levels of melatonin showed the initiation of counter inhibitory impacts on testosterone and T3 , T4 levels.”