estrogen

Examples of estrogen in the following topics:

• Extrauterine Effects of Estrogens and Progesterone

  • Like all steroid hormones, estrogen readily diffuses across the cell membrane.
  • Sex drive is dependent on androgen levels only in the presence of estrogen.
  • Estrogen plays a significant role in women's mental health.
  • Sudden estrogen withdrawal, fluctuating estrogen, and periods of sustained low levels of estrogen correlate with significant mood changes.
  • Estrogen, through estrogen receptors, upregulates the expression of progesterone receptors.

• Hormonal Regulation of the Female Reproductive Cycle

  • The menstrual cycle is controlled by a series of changes in hormone levels, primarily estrogen and progesterone.
  • Under the influence of FSH, granulosa cells begin estrogen secretion.
  • Estrogen levels will continue to increase for several days.
  • Estrogen levels are highest right before the LH surge begins.
  • This is known as a secondary estrogen surge.

• Pineal Gland and Gonads

  • Estrogen increases at the time of puberty, causing the growth of the uterus and vagina.
  • Without estrogen, egg maturation would not occur.
  • Estrogen is also responsible for secondary sex characteristics such as female body hair and fat distribution.
  • Estrogen and progesterone are responsible for the development of the breast and for the uterine cycle.
  • Male testes produce androgens, while female ovaries produce estrogen and progesterone.

• Uterine (Menstrual) Cycle

  • The levels of estrogen gradually rise, signalling the start of the follicular, or proliferation, phase of the menstrual cycle.
  • Follicular development may start but not be completed although estrogen will still stimulate the uterine lining.
  • Anovulatory flow that results from a very thick endometrium caused by prolonged, continued high estrogen levels is called estrogen breakthrough bleeding.
  • However, if it is triggered by a sudden drop in estrogen levels, it is called withdrawal bleeding.
  • High estrogen and progesterone levels stimulate increased endometrial thickness, but following their decline from a lack of implantation, the endometrium is shed and menstruation occurs.

• Aging and the Endocrine System

  • However, the effects of testosterone are not as potent as that of estrogen.
  • Estrogen acts on the nucleus of the cell by binding with the nuclear endoplasmic reticulum (ER).
  • Once it binds to the ER, a series of activation steps are initiated resulting in the binding of the estrogen-ER complex to the estrogen responsive element (ERE).
  • As a result, the effects of AD are diminished in the presence of both estrogen and testosterone.
  • Estrogen levels take a dramatic plunge with menopause.

• Female Hormones

  • As the follicles grow, they begin releasing estrogens and a low level of progesterone.
  • The level of estrogen decreases when the extra follicles degenerate.
  • After about five days, estrogen levels rise and the menstrual cycle enters the proliferative phase.
  • The level of estrogen produced by the corpus luteum increases to a steady level for the next few days.
  • Estrogen is involved in calcium metabolism and, without it, blood levels of calcium decrease.

• Ovaries

  • Ovaries secrete both estrogen and progesterone.
  • Progesterone functions with estrogen by promoting menstrual cycle changes in the endometrium.
  • Ovaries secrete estrogen, progesterone, and testosterone. 
  • Estrogen is responsible for the secondary sex characteristics of females at puberty.
  • The co-actions of progesterone and estrogen promote menstrual cycle changes in the endometrium.

• Male and Female Gonads

  • Ovaries secrete both estrogen and progesterone.
  • Estrogen is responsible for the development of the secondary sex characteristics of human females at puberty and for the maturation and maintenance of the reproductive organs in their mature functional state.
  • Progesterone functions with estrogen by promoting menstrual cycle changes in the endometrium.
  • Progesterone and estrogen are secreted by granulosal cells, whereas testosterone is produced by thecal cells.

• Female Athlete Triad: Disordered Eating, Amenorrhea, and Premature Osteoporosis

  • These gonadotropic hormones play a role in stimulating estrogen release from the ovaries.
  • Without estrogen release, the menstrual cycle is disrupted.
  • Exercising intensely and not eating enough calories can lead to decreases in estrogen, the hormone that helps to regulate the menstrual cycle.
  • Patients with female athlete triad get osteoporosis due to hypoestrogenmia, or low estrogen levels, which is part of amenorrhea.
  • With estrogen deficiency, the osteoclasts live longer and are therefore able to resorb more bone.

• Ovarian Cycle

  • Many endocrinologists believe that estrogen secretion of the dominant follicle increases to a level that indirectly lowers the levels of LH and FSH.
  • These high estrogen levels initiate the formation of a new layer of endometrium in the uterus.
  • In addition, basal body temperature may lower slightly under the influence of high estrogen levels.
  • The death of the corpus luteum results in falling levels of progesterone and estrogen.
  • Continued drops in estrogen and progesterone levels trigger the end of the luteal phase, menstruation, and the beginning of the next cycle.