Effects of excess and deficiency of thyroid hormones in the body upon blood melatonin in pubertal male rats

: Experiments have been carried out on Wistar line pubertal male rats in Winter. Radioimmunological method showed, that in intact animals the night peak of melatonin in blood was 994,36 +/- 195,99 pM/l, following ten-days intramuscular thyroxin injection (100 mg/100 g body mass)--2560,52 +/- 322,04 pM/1 and 20 days after, following bilateral thyroidectomy--117,13 +/- 16,35 pM/l, that totals 257,5% and 11,8%, respectively. Thus, the night peak of melatonin depends upon thyroid hormones concentration in blood.