title: Alterations in the proestrous pattern of median eminence LHRH, serum LH, FSH, estradiol and progesterone concentrations in middle-aged rats.
abstract: The purpose of the following study was to assess the changes in the proestrous hormone profile in middle-aged cycling rats to better understand the inter-relationship and possible interaction of these hormones during the transition to estrous acyclicity. Median eminence LHRH concentrations and serum LH, FSH, estradiol and progesterone concentrations were measured in young (3-4 months old) and middle-aged (8-10 months old) proestrous rats at 0900, 1200, 1500 and 1800h. The data demonstrate that (1) baseline hormone concentrations prior to the surge at 0900h are the same in middle-aged and young rats; (2) the proestrous gonadotropin surge is temporally delayed in middle-aged rats; (3) this delay is preceded by lower median eminence LHRH concentrations and serum estradiol concentrations at 1200h; (4) serum progesterone concentrations are lower in middle-aged rats during the preovulatory gonadotropin surge (at 1500 and 1800h) probably as a consequence of the delayed LH surge.
mesh_terms: D000375:Aging; D000818:Animals; D002940:Circadian Rhythm; D004958:Estradiol / Q000097:blood; D004971:Estrus; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism; D006728:Hormones / Q000378:metabolism*; D007986:Luteinizing Hormone / Q000097:blood; D008473:Median Eminence / Q000378:metabolism; D011247:Pregnancy; D011359:Proestrus; D011374:Progesterone / Q000097:blood; D051381:Rats
chemical_list: D006728:Hormones; D007987:Gonadotropin-Releasing Hormone; D011374:Progesterone; D004958:Estradiol; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone