Hormones of Female Reproduction

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Oogenesis and Follicular Development

• Oogenesis is the formation of gametes in the ovaries.

• Oogenesis begins before the female is born.

• A single layer of follicular cells surround each primary oocyte and are called primordial follicle.

• Primordial follicle > secondary follicle > Graafian follicle > corpus hemorrhagicum (ruptured follicle) > corpus luteum > corpus albicans.

• At ovulation, the secondary oocyte is expelled into the pelvic cavity together with the first polar cavity and corona radiata.

Hormonal Phases of Pregnancy:

Hormone synthesis in Adrenal Cortex

Follicular/Menstrual/Preovulatory Phase:

• Day 1-14.

• Day 1 = first day of bleeding.

• FSH elevated.

• Dominant follicle grows and others become atretic.

Cells of Follicle:

Theca Cells:

• Secrete androgen.

Granulosa Cells:

• Secrete estrogen and inhibin.

Circulating Estrogen:

• Inhibits the release of FSH and LH from pituitary.

• Stimulate female sex accessory organs and secondary sex characteristics.

• Proliferation of endometrial cells of uterine mucosal cells.

• Making cervix easy for sperm to traverse.

Ovulation:

• Day 14.

• Dramatic rise in estrogen.

• However, LH and FSH not inhibited from being released.

• LH: induces ovulation and corpus luteum formation.

• LH/estrogen peak: ovulation occurs.

• First meiotic division is complete and polar body released.

Luteal Phase:

• Day 14 to day 28.

Preovulatory follicle, LH surge, luteal cells:

• Granulosa and theca cells convert to luteal cells.

• Progesterone produced; LH secretion inhibited.

Progesterone functions:

• Stimulates endometrium to provide nutrition to blastocyst.

• Causes cervical mucous to seal off uterus.

• Increase BMR.

Menses:

• Endometrium is shed in a cyclic manner.

• LH inhibited by progesterone.

• Corpus luteum disposed.

• Progesterone secretion decreased, causing endometrial necrosis and menses.

Female Sex Steroid Excretion:

• Oxidation / reduction in liver.

• Glucuronide or sulfate group attached.

• Excreted in urine.

Monitoring The Menstrual Cycle:

Early follicular phase:

• Low progesterone and slowly rising estrogen metabolites.

Late follicular phase:

• Low progesterone and rapidly rising estrogen metabolites.

Luteal phase and pregnancy:

• Elevated levels of progesterone metabolites.

Next follicular cycle:

• Slowly rising FSH secretion.

Pregnancy Detection Test:

• hCG Detection in urine = pregnancy.

• Implantation = hCG is secreted.

• Detected by day 7 from conception.

Phases of Hormonal Action over Uterine Endometrium:

• Part of luteal phase before implantation; early pregnancy; late pregnancy.

Preparation for implantation (luteal phase):

• LH: causes increased progesterone and estrogen by corpus luteum.

Implantation to second month:

• hCG secreted; peaks during first 3 months.

• Increased progesterone and estrogen secretion by corpus luteum.

Third month to term:

• Placenta secretes large amounts of progesterone and estrogen to maintain uterus.

• Causes uterine growth, and growth of all components like breasts, glands, etc.

• Not under hCG control.

Parturition:

Oxytocin:

• Uterus contraction after fetus is expelled.

Prostaglandins:

• Increase uterine contractions.

Human lacation:

• Prolactin = milk secretion.

• Prolactin + estrogen + progesterone = no milk synthesis during pregnancy.

• Estrogen + progesterone = mammary gland growth only.

• Suckling required to maintain lactation; increased oxytocin, PIF/dopamine, and GnRH.

• Estrogen inhibits lactation.

Additional Readings:

Basic Endocrinology

1. Introduction to Endocrinology
2. Hypothalamic-pituitary system
3. Adrenal Hormones
4. Antidiuretic Hormone (ADH) and ECF Regulation
5. Endocrine Pancreas
6. Growth Hormone
7. Adrenal Medulla
8. Hormonal Control of Calcium and Phosphate
9. Thyroid Hormones
10. Hormones of Male Reproduction
11. Hormones of Female Reproduction
12. Fluid Compartments of the Body
13. Notes on Hypothalamus Anterior Pituitary and Thyroid
14. Additional Notes on Female Reproduction
15. Hormonal Signaling Pathways
16. FAQ on Adrenal Hormones
17. FAQ on Male Reproduction
18. Synthesis and Deficiencies of Adrenal Hormones
19. Significance of Glycosylated Hemoblogin (HbA1c)
20. Significance of Measuring Albumin while with Calcium Levels
21. Stepwise Approach to Treatment of Ascites
22. How to differentiate between Diabetes Insipidus vs Psychogenic Polydipsia

Related Topics

1. Histology of the Endocrine System
2. Histology of the Male Reproductive System
3. Histology of the Female Reproductive System

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