A Histochemical Investigation of Different Distribution of TSH Cells in Adenohypophsis of Female and Male Rats

Summary The aim of the present study was to investigate histochemically the localization of thyroid‐stimulating hormone (TSH) cells and the number of TSH cells in adenohypophysis of ovariectomized adult females, intact females at estrous and diestrous phase of sexual cycles and castrated and non‐castrated adult male rats. TSH cells, distributed throughout the pars distalis in all groups, were observed more frequent in areas near to the pars intermedia than other regions. The cells were round, ovoid, stellar‐shaped and had contacts with sinusoids. Their nuclei were large and round‐shaped. The cells were found mostly single or occasionally in groups of double and triple. The number of TSH cells was higher in estrous than diestrous phase in intact rats. In adenohypophysis of ovariectomized rats, their numbers were less than that of intacts in estrous, but higher than that of found in diestrous phases. Furthermore, the numbers of TSH cells in intact females during estrous phase was higher than those found in intact and castrated male rats. On the other hand, castration reduced the number of TSH cells while ovariectomy had no effect in this respect.