Sex Hormones & Menstruation

Androgens

Testosterone, 5-alpha dihydrotestosterone

Estrogens

Estradiol

Progestins

Progesterone

Proteins/peptides

Gonadotropin-releasing hormone (GnRH)

Gonadotropins:

• follicle-stimulating hormone (FSH)

• Lutenizing hormone (LH)

• human chorionic gonadotropin (hCG)

Other

• Prolactin

• growth hormone

• inhibin

• oxytocin

• anti-Mullerian hormone

Testosterone

• sex hormone in both men and women

• secreted by gonads + adrenal gland:

  • testes - Leydig cells

  • ovaries - Thecal cells

• Varies cyclically in men and women

  • Men: short cycle 2-4 hours, circadian cycle peaks in the morning

  • Women: peaks at ovulation in menstrual cycle

Estradiol

Synthesized from testosterone in both sexes. In women, granulosa cells in the ovaries are the main site for its production and secretion. It works with thecal cells in ovaries which secrete testosterone. Cells in brain also possess aromatase, which lets the body synthesize estrogen from testosterone

• contributes to menstrual cycle

• increases density of bone and ends growth of limb bones

• inhibition of gonadotropins

• maintains libido

Progesterone

Primarily a female hormone, present in blood at high levels during luteal phase of menstrual cycle, and during pregnancy. In men, serves primarily as intermediary metabolite in synthesis of androgens.

Oxytocin

Synthesized in the hypothalamus, transported down the axons to the posterior lobe of the pituitary gland. Present in the blood most of the time in low levels, but reaches high levels when breastfeeding, childbirth, and orgasm (in both men and women)

Gonadotropin-Releasing Hormone (GnRH)

A peptide with important sexual function as an intermediary hormone. It is produced in the hypothalamus and transported to the anterior lobe of pituitary. Stimulates the release of:

• Follicle-stimulating hormone (FSH)

• Luteinizing hormone (LH)

Prolactin

Prepares breasts for lactation and strengthens effects of other hormones

Growth hormone

Stimulates growth throughout body, plays important role at puberty (~2yr lag in males leads to height increase)

human chorionic gonadotropin (hCG)

Synthesized by the conceptus and placenta, maintains corpus luteum of the ovary

Inhibin

Secreted by gonads, acts on pituitary gland

Anti-Mullerian hormone

Secreted by the testis during fetal life by the male fetus in order to block development of the female reproductive tract in males

5-alpha-dihydro-testosterone

development and maintenance of external male genitalia and prostate gland, adult male patterns of hair distribution

follicle-stimulating hormone (FSH)

stimulates spermatogenesis and maturation of ovarian follicles

luteinizing hormone (LH)

stimulates secretion of gonadal steroids and ovulation

brain-pituitary-testis loop

Hypothalamus secretes GnRH, which stimulates the secretion of androgens by Leydig cells of testes by LH and sperm cell production in Sertoli cells by FSH. Negative feedback by testosterone on LH and GnRH and by inhibition on FSH.

menstrual, follicular, luteal

Phases of menstrual cycle in order

• breakdown of endometrium with loss of tissue and blood from the vagina (days 1-5)

• maturation of follicles in the ovaries (6-14)

• presence of a corpus luteum (15-28)

Menstrual

Endometrium is shed, triggered by a drop in progesterone levels (secreted by corpus luteum) - estrogen also drops and there is a negative feedback loop between estrogen and secretions of LH and FSH by pituitary gland

Follicular

Primary oocyte is surrounded by layer of granulosa cells (primordial follicle), which then expands and adds a layer of thecal cells (preantral follicle). A fluid-filled cavity forms within, follicle expands to ~2mm, and begins to produce gonadotropin receptors (thecal cells for LH, granulosa cells for FSH) and enlarge.

Only the dominant follicle with a receptor survives. Preovulatory follicle’s granulosa cells produce LH receptors. High estrogen levels trigger estradiol’s negative feedback on LH secretion to become positive feedback. LH levels increase ~36 hours before ovulation. Preovulatory follicle secretes progesterone, ruptures, and releases ovum.

Luteal

After ovulation, dominant follicle transforms into corpus luteum.

Granulosa cells → granulosa-lutein cells → secrete progesterone (and inhibin)

thecal cells → thecal-lutein cells → estrogen

endometrium thickens and makes it hard for sperm to penetrate

corpus luteum degenerates and progesterone/estrogen levels drop

dysmenorrhea

Painful cramps, pain in pelvis or lower back, nausea, headaches

Primary: disabling pain not associated with any diagnosable pelvic condition

Secondary: menstrual pain caused by a pelvic condition

Premenstrual syndrome (PMS)

Physical discomfort and/or negative mood change 7-14 days before period. If symptoms are severe enough to interfere with relationships, then it becomes PMDD.

Primary amenorrhea

failure to begin menstruating at puberty

menorrhagia

excessively heavy bleeding accompanied by sharp loss of iron leading to fatigue and deficiency