An overview of the past, present, and future of nongonadal LH/hCG actions in reproductive biology and medicine.

Even though there were hints, it was not until 1986 that a number of laboratories worldwide began to demonstrate unequivocally the presence and functions of luteinizing hormone/human chorionic gonadotropin (LH/hCG) receptors in various female and male nongonadal tissues. There was no species specificity but there was tissue specificity in the nongonadal LH/hCG receptor distribution. Nongonadal receptor levels were lower but they were regulated and processed and used signaling mechanisms similarly to gonadal receptors. Although still greater understanding is needed, gains made in the last decade demonstrate that nongonadal actions of LH/hCG are physiologically important and may have relevance to better understanding several diseases and their treatment. A recently developed LH receptor knockout model has begun to reaffirm and extend the importance of nongonadal LH signaling in the body.