Cyclic release of luteinizing hormone and the effects of luteinizing hormone-releasing hormone injection in Asiatic elephants.

Cyclic changes in serum concentration of luteinizing hormone (LH) were observed throughout the estrous cycle of Asiatic elephants (Elephas maximus). The increase in serum LH was correlated with a slight increase in serum estradiol concentration and the onset of behavioral heat (willingness to mate). In a second series of studies, injection of luteinizing hormone-releasing hormone after 3 days of estrone administration induced an increase in serum LH. These studies indicate that the Asiatic elephant exhibits a cyclic LH release that can be experimentally induced by estrone and luteinizing hormone-releasing hormone administration.