Notes on Female Reproductive System and Gonadotropic Axis Exploration

Male and Female Reproductive Systems

• Overview of the male reproductive system: seminal vesicle, prostate gland, ductus deferens, epididymis, testicle, glans penis, urethra, and erectile tissue.

• Overview of the female reproductive system: fimbriae, ovary, fallopian tube, endometrium, myometrium, vagina, cervix, and uterine tube.

  Exploration Biochimique de l'Axe Gonadotrope (Biochemical Exploration of the Gonadotropic Axis)

• Introduction to the exploration of the gonadotropic axis.

  Plan

• Introduction to gonads and their roles.

• Gonades féminines: Focus on female gonads (ovaries).

  I. Rappel Physiologique (Physiological Recall)

  • 1. Différenciation des gonades (Differentiation of Gonads):

  • From genotype to phenotype.

  • Sex determination occurs at three levels:

  • Chromosomal sex.

  • Gonadal sex.

  • Phenotypic sex.

  • 2. Rappel anatomo-histologique (Anatomical-Histological Recall):

  • Les ovaires (The ovaries).

  • Female reproductive system includes the vagina, uterus, fallopian tubes, and ovaries.

  Ovaries

  • Located in the abdominal cavity near the fallopian tubes; attached to the uterus via ligaments.

  • Ovaries are oval-shaped and consist of three zones:

  • Cortex: Contains follicles in various stages of development.

  • Medullary zone.

  • Vascular hilum.

  • The functional unit of the ovary is the De Graaf follicle, composed of:

  • A germ cell.

  • Surrounded by endocrine cells.

  II. Les Hormones Sexuelles Ovariennes (Ovarian Sex Hormones)

  A. La Fonction Endocrine (Endocrine Function)

• Hormone synthesis.

  B. La Fonction Exocrine (Exocrine Function)

  • Ovocyte synthesis (folliculogenesis).

  • Cycle ovarien (menstruel): Ovarian cycle/menstrual cycle:

  • A 28-day cycle divided into two phases by ovulation (day 14).

  • Phase pré-ovulatoire (pre-ovulatory phase): follicular phase.

  • Phase post-ovulatoire (post-ovulatory phase): luteal phase.

  • Cycle Duration: 24-35 days.

  • Menstruation Duration: 2-7 days.

  • occurs from puberty to menopause.

  • First menstruation: menarche.

  • Hormones stéroïdiennes (Steroid Hormones):

  • Categorized based on their receptors:

  • Glucocorticoids.

  • Mineralocorticoids.

  • Androgens.

  • Estrogens.

  • Progestogens.

  • Principales hormones stéroïdiennes humaines naturelles (Main human natural steroid hormones):

  • Glucocorticoids: cortisol.

  • Mineralocorticoids: aldosterone.

  • Sex steroids:

  • Androgens: testosterone, dehydroepiandrosterone (DHEA), dehydroepiandrosterone sulfate (DHEAS), androstenedione, dihydrotestosterone (DHT).

  • Estrogens: estradiol, estrone, estriol.

  • Progestogens: progesterone.

  • Les hormones stéroïdiennes sont toutes synthétisées à partir du cholestérol dans un processus appelé stéroïdogenèse (Steroid hormones are all synthesized from cholesterol in a process called steroidogenesis).

  B. Les Œstrogènes (Estrogens)

  • Primary female sex hormone.

  • Produced mainly by developing ovarian follicles and the placenta.

  • Small amounts are also produced by other tissues such as the liver, adrenal glands, breasts, and adipose tissue, especially important post-menopause.

  • Estrogen and diseases:

  • Hormone-dependent cancers in women (breast or endometrial cancer).

  • Protect against osteoporosis.

  • Neuroprotective effects.

  • Structure: Estrogens:

  • Natural estrogens include estrone (E1, placental), estradiol (E2, most active), and estriol (E3, produced by the feto-maternal placental unit).

  • E2 > E1 > E3 in biological effect.

  • E2 can be reversibly converted to E1.

  • Maturing ovarian follicles are the main source of estrogens, secreting more estradiol than estrone.

  • Biosynthesis: Estrogens:

  • Synthesized from androgens in the granulosa cells

  • Estetrol (E4):

  • A steroid hormone of the estrogen group; also an antioxidant.

  • Has a rather weak affinity for estrogen receptors.
    It is produced at detectable levels during pregnancy by the fetus and exclusively synthesized by the fetal liver.

  • Estetrol is closely related to estriol.

  • Transport and catabolism of Estrogens:

  • Estradiol circulates in plasma, mainly bound to SHBG (Sex Hormone Binding Globulin) and albumin. Only the free fraction is active.

  • Estrogens are transformed by conjugation into glucurono- or sulfo-conjugated derivatives in the liver and are eliminated mainly in the urine (also in bile and feces).

  • Cellular receptors:

  • Main receptors are intracellular proteins belonging to the family of nuclear receptors, coded by two distinct genes.

  • Two types of receptors: alpha (ERα) and beta (ERβ). Women possess these receptors, distributed differently depending on the organ (urogenital tract, breast, brain, bone, liver, cardiovascular system).

  • A potential third receptor, belonging to another family (G protein-coupled receptor), coded by a third gene and called GPR30, has been recently described.

  • Fonctions (Functions) of Estrogens:

  • Rôles de l’œstradiol (Roles of Estradiol):

  • Proliferative effect on target tissues and activates transcription.

  • Action on the female genital tract: maturation of the genital organs and appearance of female secondary sexual characteristics with a mitotic effect on the uterine mucosa and breast.

  • Increases endometrial thickness.

  • Increases the power and frequency of myometrial contractions.

  • Causes the appearance of cervical mucus, facilitating sperm movement.

  • Acts on the growth of the milk ducts in the mammary glands.

  • General metabolic action: increases calcium fixation and bone mineralization.

  • Retrocontrol (positive and negative) effect on the secretion of pituitary gonadotropins (FSH, LH).

  • Rôles de l’Œstrone (Roles of Estrone):

  • Estradiol reservoir, active during pregnancy.

  • Slightly anabolic.

  • Regulates gonadotropin secretion.

  • Rôles de l’Estriol (Roles of Estriol):

  • Role unknown, stimulates the growth and activity of mammary glands and prepares the endometrium for progesterone action.

  C. Progestérone

• Derived from cholesterol; precursor to steroid hormones. It’s a C21 steroid with a ketone function at C3 and a double bond between C4-C5.

  • Structure of Progesterone:

  • Biosynthesis: Progesterone:

  • Secreted into the blood from the corpus luteum and then from the placenta (after the third month of pregnancy) from pregnenolone.

  • Also produced by the adrenal cortex and the brain.

  • Transport and catabolism:

  • Progesterone circulates bound to albumin and CBG.

  • It is actively catabolized into hydrogenated derivatives (pregnanediol), which are glucurono-conjugated and eliminated in the urine.

  • Actions/Fonctions:

  • Progesterone acts via nuclear receptors (PR), type A and B, which are co-expressed in target tissues; their expression is induced by estrogens.

  • Acts on the uterus by transforming the uterine mucosa pre-stimulated by E2 into a secretory mucosa (endometrial lace) capable of accommodating a fertilized egg (nidation).

  • Inhibits uterine contractions.

  • Induces the growth of the acini of the mammary glands.

  • Causes a rise in temperature and maintains it above 37°C (+0.5°C).

  • Decreases cervical mucus, which disappears rapidly after ovulation.

• At high levels, it also has a sedative effect.

  La 17-OH Progestérone

• Also known as 17-OHP or 17α-hydroxyprogesterone, is a progestational steroid hormone chemically close to progesterone. It is also an intermediate structure in the biosynthesis of many other biological steroids, among them, androgens, estrogens, glucocorticoids and mineralocorticoids, as well as certain steroid neuromediators.

• Hydroxyprogesterone is an agonist of the progesterone receptor (with a much lower affinity).

• It increases in the third trimester of pregnancy, mainly due to fetal adrenal production.

• It is mainly produced in the adrenal glands and, to some extent, in the gonads, particularly the corpus luteum.

• The measurement of hydroxyprogesterone is useful for diagnosing patients suspected of congenital adrenal hyperplasia. Indeed, enzymatic deficiencies of 21-hydroxylase and 11β-hydroxylase (enzymatic block) lead to an accumulation of 17α-OHP.

• The 17α-OHP levels can also be used to measure the contribution of the progestative activity of the corpus luteum during pregnancy in the form of progesterone, but note that 17α-OHP is also provided by the placenta.

  Les Androgènes (Androgens)

• Testosterone.

• Δ-4-androstenedione.

• Their function is added to that exerted by adrenal androgens. It mainly affects the modification of the pilosebaceous apparatus.

• An estrogen/androgen imbalance causes seborrhea, acne, hirsutism, etc.

• They also play a likely role in maintaining libido.

• Remarque (Note):

• DHEA and S-DHEA are weak androgens of adrenocortical origin.

  Les Peptides Ovariens (Ovarian Peptides)

• They are very numerous. Among these factors, we can mention:

• Cytokines: Interleukin-1β, Tumor Necrosis Factor α (TNFα).

• Growth factors: Insulin Growth Factor-1 (IGF-1) and Insulin Growth Factor-2 (IGF-2) associated with their carrier proteins IGFBPs, Epidermal Growth Factor (EGF), Transforming Growth Factor-β (TGF-β), Fibroblast Growth Factor-2 (FGF-2).

• Peptides of oocyte origin: GDF-9, c-Kit.

• Peptides synthesized by the granulosa: Anti-Müllerian hormone (AMH), activins, inhibins, KitLigand.

  Les Inhibines A et B (Inhibins A and B)

• Inhibins are heterodimeric glycoproteins consisting of two chains, α and β, linked by a disulfide bridge.

• The β A chain is specific to Inhibin A (Inh A).

• The β B chain is specific to Inhibin B (Inh B).

• The α chain is common to Inh A and Inh B.

• Inhibine B (Inhibin B):

• Secreted by the cohort of follicles (granulosa) at the beginning of the follicular phase.

• The level of inhibin b is a reflection of ovogenesis (inhibin decreases with age).

• Inhibin b inhibits FSH.

• Its measurement is used as a marker of follicular recruitment and ovarian reserve.

• Inhibine A (Inhibin A):

• Secreted during the luteal phase and the first months of pregnancy (it inhibits a possible ovulation).

  AMH (Hormone Anti-Müllérienne)

• A glycoprotein of the transforming growth factor beta (TGF-β) family, it is involved in sexual differentiation during embryogenesis.

  • In non-menopausal adult women, AMH is secreted by granulosa cells of preantral and antral follicles and is involved in the regulation of follicular development by curbing the cyclical recruitment of growing follicles and modulating granulosa cell sensitivity to follicle-stimulating hormone (FSH).

  • A quantitative marker of ovarian reserve.

  • The AMH level remains constant throughout the ovarian cycle but decreases with age.

  B. Fonction Exocrine (Exocrine Function)

  Ovogénèse et cycle ovarien (menstruel) (Ovogenesis and ovarian (menstrual) cycle)

• They constitute the site of the ovarian reserve (follicles) which evolve according to a process known as folliculogenesis including the menstrual cycle which marks puberty.

  Folliculogenèse (Folliculogenesis)

• A complex process that starts during the embryonic period and ends during a menstrual cycle. The primary ovocyte must evolve and pass through different stages before becoming the ovulated ovocyte ready to be fertilized.

• Réserve ovarienne (Ovarian Reserve):

• Forms from the fourth month of fetal life.

• Includes primordial, intermediate, and small primary follicles.

• At birth, approximately 1 million primary oocytes regresses.

• At puberty, ovaries contain ≈ 400,000 ovocytes; 400 to 500 reach maturity for possible fertilization between puberty and menopause.

• L'ovogenèse démarre à la puberté sous l’impulsion hormonale (Ovogenesis begins at puberty under hormonal impulse).

• Cyclical hormonal activity, each cycle ≈ 28 days.

• The menstrual cycle shows the integrity of the gonadotropic axis (CNS, hypothalamus, pituitary gland, ovaries) and genital tract (uterus, vagina).

• This cycle is separated into two phases by ovulation:

• Phase folliculaire (Follicular Phase): Growth of a dozen follicles with the maturation of one follicle (de Graaf).

• Divided into two parts: Early follicular phase – selection of the dominant follicle (approximately 5 days) and Late follicular phase J6-J13. The menstrual phase lasts 4 days and marks the beginning.

• Phase ovulatoire (Ovulatory Phase): fourteenth day of the cycle.

• Phase lutéale/post-ovulatoire (Luteal/Post-Ovulatory Phase): Completes the cycle with the development of the corpus luteum, which persists for 10 to 14 days in the absence of gestation and then degenerates.

  2. Régulation hormonale du cycle ovarien (Hormonal Regulation of the Ovarian Cycle)

• The regulation of the ovarian cycle involves the hypothalamic-pituitary-ovarian axis

  • Hypothalamus: GnRH - Gonadotropin-releasing hormone.

  • Hypophysis: FSH, LH - Gonadotropins.

  • Ovaries: Estrogens, progesterone, inhibin B and AMH, etc.

  GnRH (LH-RH)

• Hypothalamic decapeptide neurohormone.

• Secreted as a pre-pro hormone of 92 amino acids, cleaved into GnRH and GAP (GnRH-Associated Peptide).

• Acts on gonadotropic cells via a specific G protein-coupled receptor.

• Stimulates the synthesis and secretion of FSH and LH by the adenohypophysis.

• Secreted in a pulsatile manner, allowing preferential secretion of FSH or LH depending on the cycle; every 90 minutes during the follicular phase and every 3-4 hours during the luteal phase.

• Secretion influenced by sex steroids, glutamate, GABA, norepinephrine, leptin, kisspeptins

  L’hormone folliculo-stimulante « FSH » (Follicle-Stimulating Hormone “FSH”)

• 35 KD pituitary heterodimeric glycoprotein, composed of 2 subunits α and ß, with α (89 aa) common to FSH, LH, hCG, TSH, and ß (118 aa) specific to the hormone.

• Secretion is controlled by GnRH, ovarian estrogens, progesterone, and inhibin B; continues secretion.

• It acts via G protein-linked receptors expressed on granulosa cells: activation of aromatase responsible for the conversion of androgens to estrogens.

• Promotes and supports the growth of ovarian follicles and the selection of the dominant follicle.

• Stimulates the synthesis of its own receptor in granulosa cells.

  L’hormone lutéinisante « LH » (Luteinizing Hormone “LH”)

• 35 KD pituitary heterodimeric glycoprotein, composed of 2 subunits α and ß, with α (89 aa) common to FSH, LH, hCG, TSH, and ß (115 aa) specific to the hormone.

• Secretion is controlled by GnRH and ovarian estrogens.

• Secreted in pulsatile mode.

• Acts via G protein-linked receptors, which also bind hCG.

• Stimulates the synthesis of androgens by theca cells of the ovary.

• Triggers ovulation (by stimulating a cascade of proteolytic enzymes, leading to the rupture of the basement membrane of the follicle).

• Maintains the corpus luteum during the menstrual cycle.

  The Prolactine

• A peptide hormone.

• Several circulating forms: monomeric prolactin (mPRL), glycosylated prolactins, big-prolactin (bPRL) – a mix of dimers and trimers of glycosylated prolactins, and big-big prolactin (bbPRL or macroprolactin) – prolactin linked to IgG.

• Secreted by lactotroph cells of the anterior pituitary and controlled by both central (hypothalamus) and peripheral (gonads, thyroid) factors.

• Pulsatile and cyclical secretion.

• Unlike other anterior pituitary hormones, hypothalamic control is primarily inhibitory; the responsible substance, long called PIF (prolactin inhibiting factor), is dopamine.

Actions Physiologique (Physiological Actions)

• Has mammotrophic (mammary gland growth).

• Lactogenic (milk synthesis stimulation).

• Libidinal effects.

• Angiogenic role in blood vessel formation.

  III. La Puberte (Puberty)

• The set of physical and psychological phenomena defining the transition from childhood to adulthood, leading to the acquisition of definitive size and reproductive function.
  Changes Hormonaux Pubertaires (Pubertal Hormonal Changes):

• Appearance between ages 8 and 13.

• Adrenal androgen production starts before menarche (gonadal puberty).

• DHEA and SDHEA secretion increases from age 7-8, causing the appearance of secondary sexual characteristics (pubic hair, breast enlargement, acne, etc.).

IV. La Ménopause (Menopause)

• Physiological phenomenon occurring around age 51 (on average) in all women's lives.
  Permanent disappearance of menstruation, secondary to the cessation of ovarian function.

  Symptomatologie (Symptoms):

• Sweats (especially nocturnal) and hot flashes.

• Joint pain.

• Asthenia (weakness).

• Mood and sleep disorders.

• Memory loss.

• Decreased libido and vulvo-vaginal dryness.

  Biologie (Biological):

• Increased FSH with normal LH levels; eventually, both FSH and LH increase permanently.

• Decreased estrogen and progesterone levels.

  V. Exploration biologique (Biological Exploration)

• 1. Les dosages statiques (Static dosages).

• 2. Les dosages dynamiques (Dynamic dosages).

  1 . Les dosages statiques (Static dosages):

• Prélèvement (Collection):

  • Sang (Blood): sérum ou plasma (serum or plasma).

• Paramètres à doser (Parameters to measure):

  • FSH, LH, Progestérone, œstradiol, Testosterone, Prolactine, AMH, Inhibine, Delta 4 androstènedione, 17 OHP, DHEA et S-DHEA.

• FSH

  • collection

    • tube sec/heparin

    • collection between day 2 and 5 of cycle or any day if amenorrhea

    • collect in the morning

  • Dosage done vis “sandwich” method

  • indicate when prescribing for hypofertility or trouble with the puberty

• LH

  • Collection

    • Plasma concentration change with pulsatile secretion

  • Dosage done via the “sandwich” method

  • Indicate when prescribing in the context of a therapeutic follow-up during periovulatory period

• Estradiol

  • Dosage using the “competition” method

• Progesterone

  • collection

    • collect on the 21st day of cycle

  • Dosage use “competition” method.

  • Indication

    • Evaluate the lunar phase quality

    • After an embryo replacement follow progress of growing rate progesterone

2 . Les dosages dynamiques (Dynamic dosages):

• Test à la LHRH (GnRH) (LHRH (GnRH) Test).

  • Explore la fonction gonadotrope hypophysaire (Explores pituitary gonadotropic function).

• Test au clomifène (Clomid®) (Clomiphene Test).

• Test au tamoxifène (Tamoxifen Test).

• Test de stimulation à l’hormone Chorionique Gonadotrope (HCG) : Test à l’Ovitrelle® (Human Chorionic Gonadotropin (HCG) Stimulation Test: Ovitrelle® Test).

  VI. Pathologies (Pathologies)

• Aménorrhée (Amenorrhea):

  • Primaire (Primary):

    • Absence de caractères sexuels secondaires (Absence of secondary sexual characteristics).

      • Hypogonadisme hypergonadotrophique (Hypergonadotrophic hypogonadism).

      • Hypogonadisme hypogonadotrophique (Hypogonadotrophic hypogonadism).

  • Secondaire (Secondary):

    • Présence de caractères sexuels secondaires (Presence of secondary sexual characteristics).

  • Etiologies

  • Idiopathique.

  • Activation prématurée de l’axe hypothalamo-hypophysaire (Premature activation of the hypothalamic-pituitary axis).:

  • Tumeurs hypothalamiques (Hypothalamic tumors).

  • Méningites (Meningitis).

  • Hydrocéphalie (Hydrocephalus).

  • Tumeurs surrénaliennes, ovariennes, à hCG (Adrenal tumors, ovarian tumors, hCG-producing tumors).

• Puberté précoce : early puberty

  • PPC: Puberté Précoce Central:: central precocious puberty

  • peripheral precocious puberty: oPeripheral origination, 2 forms:

    • Test à la LHRH: uses LHRH test to determin type

      • puberty central: réactivité response prédomine en LH qui s’élève au- delà de 5 mUI/ml ± un ratio LH/FSH > 1

      • puberty peripherique: réactivité de response en FSH et LH est faible ou nulle.

  • Hyperandrogénie (Hyperandrogenism):

  • Étiologies: *.SOPK: syndrome des ovaries polycystic *Hyperplasie congénitale des surrénales

    • Cause tumoural(Leydig tumor)
      *.Hirsutisme idiopathique