Concentrations of luteinizing hormone in the plasma or hemicastrated cockerels.

The concentrations of LH in plasma were measured, using a radioimmunoassay, during sexual development of intact cockerels and cockerels hemicastrated at 2 weeks of age. The pattern of LH secretion during maturation was characterized by a series of at least four consistently observed periods of rising and falling blood levels of the hormone. Levels of luteinizing hormone were higher in hemicastrated than in intact cockerels between 2 and 4 weeks after the operation (4--6 weeks of age) and then fell to values below those seen in intact cockerels between 8 and 11 weeks of age. Thereafter, until 28 weeks of age, levels of LH in plasma in both hemicastrated and intact birds were similar. The transient changes in LH concentration after hemicastration were thought to be a direct consequence of an alteration in the concentration of testicular steroids in the blood after the removal of one gonad.