ENDOCRINOLOGY
This is a review only of those hormones of interest in reproduction.
Hypothalamus
Gonadotropin releasing hormone (GnRH) - protein hormone; stimulates release of LH and FSH
Pituitary
Posterior lobe
Oxytocin - protein hormone; stimulates mammary gland to cause milk letdown; causes contractions of gravid uterus at parturition and contributes to cervical dilation
Anterior lobe
Follicle stimulating hormone (FSH) - protein hormone; stimulates growth of follicle on ovary; in male induces formation of androgen binding protein that maintains high intratesticular testosterone concentrations
Luteinizing hormone (LH) - protein hormone; also known as interstitial cell stimulating hormone; causes ovulation of mature ovarian follicles; maintains CL on ovary after ovulation; stimulates and sustains testosterone release and spermatogenesis in testes
Prolactin - protein hormone; stimulates milk production in mammary gland; induces maternal behavior
Ovary
Follicle
Estrogen - steroid hormone; stimulates female sexual development; decline during estrus causes behavior of "standing heat"
Corpus luteum (CL)
Progesterone - steroid hormone; responsible for pregnancy maintenance; decreases uterine contractility; stimulates development of mammary tissue and endometrium; induces maternal behavior
Placenta / Pregnancy-specific tissues
Dog
Relaxin - protein hormone; relaxes pubic symphysis and contributes to cervical dilation late in gestation; may be produced in the ovary as well
No pregnancy-specific gonadotropins are produced. All progesterone for pregnancy maintenance is produced by the CL.
Cat
No pregnancy-specific gonadotropins are produced. Progesterone for pregnancy maintenance produced by CL and may be produced by fetal/placental unit.
Human
Human chorionic gonadotropin (hCG) - protein hormone; produced by fetal/placental unit, has LH activity in other species
Horse
Equine chorionic gonadotropin (eCG) - protein hormone; produced by endometrial cups, has FSH and/or LH activity in other species
Cow
No pregnancy-specific gonadotropins produced. Progesterone for pregnancy maintenance produced by CL, adrenals, fetal/placental unit.
Testis
Testosterone - steroid hormone; stimulates male sexual development and behavior, spermatogenesis
Mullerian inhibiting factor (MIF) - protein hormone; secreted only during embryogenesis;
inhibits female duct development