Reproductive Hormones

Gonadotropin-releasing Hormone (GnRH)

• Source: Hypothalamus

• Targets and Functions:

  • Females and Males: Anterior Pituitary

  • Stimulates the production of Follicle stimulating Hormone and Luteinizing Hormone.

  • Regulates the release of FSH and LH by the anterior pituitary gland

Follicle Stimulating Hormone (FSH)

• Source: Anterior Pituitary

• Targets and Functions:

  • Females - Ovaries

    • Stimulates follicle growth and maturation

    • Stimulates estrogen production

  • Males - Seminiferous Tubules

    • Promotes sperm production by establishing testosterone receptors on tubules

Luteinizing Hormone (LH)

• Source: Anterior Pituitary

• Targets and Functions:

  • Females - Ovaries

    • Stimulates primary oocyte to complete first meiotic division to become secondary oocyte

    • Triggers ovulation of secondary oocyte

    • Transforms ruptured follicle into corpus luteum

    • Stimulates production of progesterone by corpus luteum

  • Males - Seminiferous Tubules

    • Stimulates sperm production by causing interstitial cells in testes to secrete testosterone

Estrogen

• Sources: Maturing Follicles and Corpus Luteum

• Targets and Functions:

  • Body in general - Stimulates the development of female secondary sexual characteristics

  • Uterus - Stimulates proliferatvie phase of uterine cycle

  • Ovaries - Promotes oogenesis

  • Breasts - Stimulates development of milk ducts and sinuses (ampullae)

  • Anterior Pituitary - Stimulates burst-like release of LH

Progesterone

• Source: Corpus Luteum and Placenta

• Targets and Functions:

  • Females - Uterus

    • Maintains thickened endometrium

    • Stimulates nutrient release

    • Quiets myometrium

  • Females - Breasts

    • Stimulates development of alveoli for milk production

  • Females - Anterior Pituitary

    • Inhibits production and release of FSH and LH

Testosterone

• Source: Interstitial Cells in Testes

• Targets and Functions:

  • Body in general - Stimulates the development of male secondary sexual characteristics including:

    • Development of male genitalia

    • Male skeleton and muscle development

    • Male patterns for hair growth

    • Increased RBC production and higher metabolic rate

  • Seminiferous Tubules - Necessary for the completion of spermatogenesis

  • Anterior Pituitary - Moderate inhibition of pituitary and hypothalamus

Oxytocin

• Sources: Manufactured by hypothalamus. Stored and released by Posterior Pituitary.

  • Positive Feedback Mechanisms:

    • Childbirth - Stretching of uterus and cervix

    • Suckling - Milk letdown reflux

• Targets and Functions:

  • Uterus - Stimulates contraction of uterine myometrium causing lowering of fetus and labor.

  • Breasts - Stimulates contraction of milk ducts and sinuses, releasing milk.

Prolactin

• Source: Anterior Pituitary

• Targets and Functions:

  • Breasts - Stimulates alveoli of breasts to produce milk

  • Regulation - Release of prolactin by anterior pituitary is regulated by hypothalamus production of Prolactin Releasing Hormone (PRH) and Prolactin Inhibiting Hormone (PIH)

Human Chorionic Gonadotropin

• Source: Trophoblasts of blastocyt and Chorion

• Targets and Functions:

  • Corpus Luteum - Maintains corpus luteum and causes it to continue producing progesterone in the absence of LH through first four months of pregnancy till placenta produces sufficient estrogen and progesterone to maintain the pregnancy.