Effect of Exogenous Melatonin on Thyroxin e (T 4 ), Thyrotropin (TSH) Hormone Levels and Expression patterns of Melatonin Receptor (MT1 and MT2) Proteins on Thyroid gland during Different age groups of Male and Female Swiss albino Mice

The pineal gland hormone melatonin regulates diverse endocrine activities such as thyroid hormone regulation during different physiological condition of the organism. Melatonin exerts most of physiological activities thro ugh its membrane bound MT1 and MT2 receptors. The present research was carried out to study the effects of exogenous melatonin on thyroxin e (T 4 ), thyrotropin (TSH) hormone levels and expression patterns of melatonin receptor (MT1 and MT2) proteins on thyroid gland during different age groups (2 months, 4 months and 8 months) of male and female Swiss albino mice. In male mice group, melatonin treatment can cause the inhibition of T 4 hormone via unaltered TSH level during 2 months and 4 months age group, but in 8 months it increased the level of T 4 as well as TSH level. In female mice group, melatonin elevated the level of T 4 through unaltered the level of TSH during all age groups of mice. However melatonin also significantly decreased the MT1 receptor p roteins expression of thyroid gland in both male and female mice. Whereas MT2 receptor proteins of thyroid gland were expressed differentially due to melatonin supplementation during different age groups of male and female mice. The findings of our present study suggested that melatonin age and sex differentially effects on T 4 hormone. The present study also suggested that melatonin might be prefers its MT2 receptors present on thyroid gland for regulation of T 4 hormone secretion which also depends on age a nd sex (male or female) of