| Abstract: | Thyroid activity, pituitary and serum thyrotrophic potency in response to the administration of clomid, sexovid, PGE1 and PGF2alpha, were studied in H. fossilis. Hightened thyroidal activity and CR (conversion ratio of PB 131I in blood serum in relation to total serum 131I uptake) were noticed a week after clomid (150 microgram/fish/day) and sexovid (150 microgram/fish/day) treatment. Clomid and sexovid also elevated the serum thyrotrophic potency although pituitary TSH level was unaffected. It is evident from the results that clomid and sexovid either act via hypothalamus or directly over pituitary to increase TSH secretion followed by increased thyroid activity. PGE1 and PGF2alpha (100 microgram/fish/day, each) administration increased thyroidal 131I uptake but failed to stimulate hormone output from thyroid gland. Increased TSH level in blood and decreased level of TSH in pituitary was observed in response to the above prostaglandins. It seems that PGE1 and PGF2alpha inhibit thyroid hormone secretion like anti-thyroid drugs triggering the release of TSH into blood. |
