Gonadal hormones (Testosterone, Estrogen, Progesterone, Activins and Inhibins).pptx

*Gonadal hormones
*Testosterone
*How is Testosterone controlled?
*Ovarian Hormones
*Estrogen
*Progesterone
*Activins and Inhibins

1. Gonadal Hormones Gonads: The gonads, the primary reproductive organs, are the testes in the male and the ovaries in the female. These organs are responsible for producing the sperm and ova, but they also secrete hormones and are considered to be endocrine glands. Gonadal hormones are hormones produced by the gonads, and include both steroid and peptide hormones . The major steroid hormones include ESTROGEN and PROGESTERONE from the OVARY, and TESTOSTERONE from the TESTIS. The major peptide hormones include ACTIVINS and INHIBINS

2. Testosterone Testosterone is produced by the gonads ( by  testes in men and by the ovaries in women), although small quantities are also produced by the adrenal glands in both sexes. It is an androgen, meaning that it stimulates the development of male characteristics. Women also produce testosterone, but at lower levels than men . Testosterone initiates the development of the male internal and external reproductive organs during foetal development and is essential for the production of sperm in adult life.

3. During puberty, testosterone is involved in many of the processes that transition a boy to manhood, including: Healthy development of male sex organs Growth of facial and body hair deepening of the voice Increase in height Increase in muscle mass Growth of the Adam’s apple The importance of testosterone is not limited to puberty. Throughout adulthood, the hormone is integral in a variety of functions, such as : Sperm production Maintaining muscle strength and mass Promoting healthy bone density Making new blood cells

4. How is testosterone controlled ? The hypothalamus and pituitary gland control how much testosterone the testes produce and secrete . The hypothalamus releases gonadotropin-releasing hormone which stimulate pituitary gland to release gonadotrophic hormones (follicle stimulating hormone and luteinizing hormone). Gonadotrophic hormone stimulates testosterone production. If too much testosterone is produced, the hypothalamus alerts the pituitary gland to make less LH, which tells the testes to decrease testosterone levels .

5. Ovarian Hormones The ovary is the primary source of gonadal hormones in women during the childbearing years (i.e. between puberty and menopause). When properly regulated by follicle-stimulating hormone (FSH) and luteinizing hormone (LH) from the pituitary, each menstrual cycle consists of the following events: A follicle in the ovary matures, secretes increasing amounts of estrogen, releases an ovum, and is transformed into a progesterone-secreting corpus luteum. If the ovum is not fertilized and implanted, the corpus luteum degenerates; the uterine endometrium (lining of the uterus) is shed as part of the menstrual flow, and the cycle repeats.

6. Estrogen Estrogen is a steroid hormone that promotes female sexual development and stimulates the growth and maturation of primary and secondary sex characteristics. Men have estrogen, too, but in smaller amounts. In males estrogen helps in maturation of the sperm. Estrogen helps bring about the physical changes that turn a girl into a woman. This time of life is called puberty. These changes include: Growth of the breasts Growth of pubic and underarm hair Start of menstrual cycles Estrogen helps control menstrual cycles and is important for childbearing

7. Estrogen also has other functions: Keeps cholesterol in control Protects bone health for both women and men Affects your brain (including your mood), bones, skin and other tissues. Our body produces three main types of estrogen: Estradiol (E2): the most common type in women of childbearing age Estriol (E3): the main estrogen produced during pregnancy. Estrone (E1): produced after menopause – when menstrual periods stop.

8. Progesterone Progesterone is a steroid hormone. It is secreted by the corpus luteum, a temporary endocrine gland that the female body produces after ovulation during the second half of the menstrual cycle. Progesterone prepares the endometrium (lining of the uterus) for potential pregnancy after ovulation. It triggers the lining to thicken to accept a fertilized egg. It also prohibits the muscle contractions in the uterus that would cause the body to reject an egg. It the woman does not become pregnant, the corpus luteum breaks down, lowering the progesterone levels in the body. This change initiate menstruation.

9. If the body does conceive, progesterone continues to stimulate the body to provide the blood vessels in the endometrium that will feed the growing fetus. Once the placenta develops, it also begins to secrete progesterone, supporting the corpus luteum. This causes the levels to remain elevated throughout the pregnancy, so the body does not produce more eggs. It also helps prepare the breasts for milk production.

10. Activins and Inhibins Both activin and inhibin are peptide hormones and released by gonads (i.e. testes and ovaries). Both are involved in the regulation of Follicle stimulating hormone of pituitary gland. Activin stimulate/activate follicle stimulating hormone (FSH) release by the pituitary gland. I nhibin inhibits FSH production . Inhibin is antagonist of FSH. Inhibin has a negative-feedback effect on the anterior pituitary to reduce FSH secretion.