Effect of thymectomy on serum gonadotrophins and testosterone concentration

There is controversy about the relationship between thymic secretion and secretion of gonadotrophins and testosterone. One group of scientists reported that thymus is stimulatory to gonadotrophins and testosterone secretion, and according to other group thymic secretion is inhibitory to gonadotrophins and testosterone secretion. So we tried to observe what exactly happens to serum gonadotrophins and testosterone level following thymectomy. Thymectomy was performed in prepubertal animals and after 45 days of their operation serum gonadotrophins were measured by ELISA technique and serum testosterone was measured by RIA technique. The present study reveals a significant fall in serum FSH level along with significant rise in serum LH and testosterone level in male albino rats following thymectomy in comparison to that of sham thymectomized rats. It appears that thymus has an inhibitory influence on LH secreting gonadotrophs which has been withdrawn following thymectomy and as a result there occurs an increase in serum LH level. This LH stimulates interstitial cells of leydig and cause thereby an increase in serum testosterone level. The result also gives an indication that among the gonadotrophs in pituitary, one type is concerned with the secretion of LH while some gonadotrophs are concerned with secretion of FSH only; and the thymus possibly maintains the FSH secreting gonadotrophs intact at least till the age of puberty. Thymectomy may cause some disorganization of FSH secreting gonadotrophs which results in the fall in serum FSH level in thymectomized animals in comparison to that of sham thymectomized animal group.