ABSTRACT
The present study was designated to clarify the effect of calcitonin [CT] on the hypophysial testicular axis. A total number of forty adult male albino rats were used and they were classified into three main groups. The first group [control group] consisted of 10 adult male albino rats, which were injected intramuscularly with saline allover the period of experiment. The second group: [sCT-, administered group] consisted of 10 adult male albino rats, which were injected with sCT intramuscularly on alternative days, in a dose of 10 U/kg body weight/days for 4 weeks at 10 AM. However the third group [orchidectomized group consisted of 20 adult male rats. This third group was subdivided into two equal groups: Orchidectomized control group which was injected intramuscularly with saline, two weeks after the operation, for four weeks and Orchidectomized CT-administered group which were injected intramuscularly with sCT, two weeks after the operation, on alternative days in a dose of 10 U/kg body weight day for 4 week at 10 AM. The plasma levels of FSH, LH and testosterone were estimated [by radioimmunoassay] and the Ca[2+] plasma levels were estimated [by Clorometric method] for all groups. Also, histopathological examination was performed for the testes of the first and second groups to evaluate the local effect of CT and also to identify the effect of change in plasma gonadotropin levels on the testes.The results of these investigations showed that, the testosterone plasma levels were significantly decreased in healthy group after sCT administration, the FSH and LH plasma levels were significantly decreased in both healthy and orchidectomized groups after sCT administration and sCT administration caused insignificant change in Ca[2+] plasma levels in both healthy and orchidectomized groups after sCT administration. The histopathological study revealed that sCT administration caused thickening of the basement membrane of the seminiferous tubules in 20% of the total number of rats treated with sCT, thickening of the basement membrane and replacement of the interstitial cells of Leydig by halonosis in 50% of the total number of rats treated with sCT and thickening of the basement membrane, replacement of the interstitial cells of Leydig by halonosis and spermatic arrest at the stage of secondary spermatocytes in 30% of the total number of rats treated with sCT. From the above results, it could be concluded that CT administration resulted in a significant reduction in testosterone plasma levels that may be through a reduction in pituitary gonadotropins secretion and through a direct effect on the testes