Genetics and Luteinizing Hormone Receptors

Testicular luteinizing hormone receptors (LH-Rs) that bind either LH or human chorionic gonadotropin (hCG) are required for the differentiation of the Leydig cell (1). This is indicated by the correlation between the onset of Leydig cell differentiation and the appearance of hCG during the development of the human fetus. The number of Leydig cells also correlates with the levels of hCG during pregnancy. Leydig cells, and therefore LH-Rs, are present by week 8 of pregnancy in the human (2–4), and by day 15 in rodents (5).