In the present investigation exogenous administration of calcium or
(hCG) to mature male chickens chorionic gonadotropin human modulated the secretions and correlations between different reproductive hormones, either pituitary or gonadal hormones. A stimulatory effect on thyroid gland with an adverse effect on testicular activity were observed with calcium administration, while an inhibitory effect on thyroid gland with a stimulatory effect on testicular activity were observed with hCG administration. So, it is advisable to use calcium or hCG in poultry farm, especially in mature male birds, with caution. Further studies on the use of calcium in combination with hCG should be taken in considerations.