Pituitary and testicular activity in chickens after embryonic testosterone treatment

This study was conducted to explain the lower circulating testosterone levels in chickens exposed to testosterone propionate (TP) on the 3rd day of incubation. Control and TP males were injected with either luteinizing hormone (LH) or gonadotropin-releasing hormone (GnRH). Testosterone (T), dihydrotestosterone (DHT), and LH were measured by radioimmunoassay. Levels of circulating T in 20-wk-old TP males were significantly lower than controls, but the response to GnRH was similar in both groups. LH levels were also similar. Testosterone responses to LH in 20-wk-old TP males were lower than controls, possibly due to their lower initial T concentrations. Pituitary extracts from TP and control birds showed similar abilities to induce testicular 32P uptake in day-old cockerels. The data demonstrate that the anterior pituitary gland and testes of TP birds are capable of responding to GnRH and LH, respectively. The TP males are defective in that they fail to produce testosterone, which may reflect a reduced concentration of LH receptors in their testes.