Sex Hormones

Free Online Lectures of Biochemistry for Medical, Dental and Allied Health Sciences by Biochemistry Club

The Sex hormones are secreted by the gonads in response to Pituitary Gonadotropins (LH and FSH)

These are:

1. Estrogen
2. Progesterone and
3. Testosterone

Ovarian Hormones

• Ovarian hormones are C18 estrogens, C19 androgens and C21 progesterone.
• These are produced by the ovarian follicles.
• The Follicular thecal cells produce C19 androgens.
• These C19 androgens are then converted to C18 estrogens by granulosa cells, by aromatization of ring A and loss of C19 methyl group.
• Estradiol is the most important estrogen.
• It is then converted to estrone by liver.
• It is further hydroxylated to estriol, which is inactive.
• Estradiol is bound to plasma SHBG (Sex Hormone Binding Globulin).
• Estradiol (E2) is the predominant sex hormone present in females; But, it is also present in males, at lower levels..
• Estradiol has not only a critical impact on reproductive and sexual functioning, but also affects other organs including the bones.
• Estradiol enters cells freely and interacts with a cytoplasmic target cell receptor;
• Then it enters the nucleus of the target cell, and regulates gene transcription.
• Estradiol binds with equal affinity to both estrogen receptors ER-alpha & ER-beta.
• Selective Estrogen Receptor Modulators (SERMs) preferentially act on one of these receptors.

Regulation of Ovarian Hormones

• FSH influences follicles to ripen, which produces estrogen.
• Estrogen level gradually increases in the second week of the menstrual cycle.
• Estrogen level is maximum 24 hours before the LH peak.
• High doses of estrogen can suppress the LH release and, therefore effective as contraceptive.
• Under the influence of Estrogen, uterine endometrium proliferates. Glands in endometrium are hypertrophied.
• Ducts in mammary glands are proliferated and progesterone receptors are synthesized.
• LH level peaks 16 hours before the ovulation.
• The LH surge induces the ovulation.
• The corpus luteum then starts secreting progesterone.
• Under the influence of progesterone, endometrium enters the secretory phase, and prepares for implantation of the fertilized ovum.
• LH is required for maintenance of corpus luteum.
• If implantation occurs (day 22–24), the LH function is taken over by the …

All these lectures are organized and listed in detail in their proper sections. To view these lessons please visit the Hormones & Signal Transduction Section. This can be approached by directly clicking the Biochemistry II button or it can also be approached from the drop down menu in Biochemistry II tab. Once you reach the section click the curriculum tab to view the full list in the section.

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