Hormones

• Hormones produced by the reproductive glands (gonads)


  • Testosterone
  • Estrogen
• Testosterone


  A steroid hormone from the androgen group found in mammals, reptiles, birds, and other vertebrates
• Testosterone


  • Primarily secreted in the Leydig cells of the testes of males and the ovaries of females, although small amounts are also secreted by the adrenal glands
  • The principal male sex hormone and an anabolic steroid
  • Plays a key role in the development of male reproductive tissues and promoting secondary sexual characteristics
  • Essential for health and well-being as well as the prevention of osteoporosis
  • Adult human males produce about ten times more testosterone than adult human females, but females are more sensitive to the hormone
  • Levels demonstrate circadian pattern and peak at the time of awakening (7AM), fall to their lowest level at 8PM
• Testosterone effects


  1. Virilizing effects

  2. Anabolic effects
• Anabolic effects of testosterone

  • Growth of muscle mass and strength
  • Increased bone density and strength
  • Stimulation of linear growth and bone maturation
• Androgenic effects of testosterone

  • Maturation of the sex organs, particularly the penis and the formation of the scrotum in the fetus
  • Deepening of the voice
  • Growth of the beard and axillary hair
  • Many of these fall into the category of male secondary sex characteristics
• Testosterone effects by age of occurrence

  • Prenatal
  • Early infancy
  • Pre-peripubertal
  • Pubertal
  • Adult
• Prenatal androgen effects


  1. Genital virilization

  2. Development of prostate and seminal vesicles

  3. Gender identity
• Early infancy androgen effects

  Testosterone levels rise in the first weeks of life for male infants, remain in a pubertal range for a few months, but usually reach the barely detectable levels of childhood by 4–6 months of age. The function of this rise in humans is unknown, but it has been speculated that "brain masculinization" is occurring.
• Pre-peripubertal androgen effects


  • Adult-type body odour
  • Increased oiliness of skin and hair, acne
  • Pubarche (appearance of pubic hair)
  • Axillary hair
  • Growth spurt, accelerated bone maturation
  • Hair on upper lip and sideburns
• Pubertal androgen effects


  • Enlargement of sebaceous glands, which might cause acne
  • Phallic enlargement or clitoromegaly
  • Increased libido and frequency of erection or clitoral engorgement
  • Pubic hair extends to thighs and up toward umbilicus
  • Facial hair (sideburns, beard, moustache)
  • Loss of scalp hair (Androgenetic alopecia)
  • Chest hair, periareolar hair, perianal hair
  • Leg hair
  • Axillary hair
  • Subcutaneous fat in face decreases
  • Increased muscle strength and mass
  • Deepening of voice
  • Growth of the Adam's apple
  • Growth of spermatogenic tissue in testicles, male fertility
  • Growth of jaw, brow, chin, nose, and remodeling of facial bone contours
  • Shoulders become broader and rib cage expands
  • Completion of bone maturation and termination of growth
• Adult testosterone effects


  • Necessary for normal sperm development
  • Regulates acute HPA (Hypothalamic–pituitary–adrenal axis) response under dominance challenge
  • Mental and physical energy
  • Maintenance of muscle trophism
  • Regulates the population of thromboxane A2 receptors on megakaryocytes and platelets and hence platelet aggregation
  • Libido as evinced in clitoral engorgement/penile erection frequency
  • Does not cause or produce deleterious effects on prostate cancer
  • Plays a role in the regulation of the fight-or-flight response
  • Falling in love decreases men's testosterone levels while increasing women's testosterone levels
  • Plays a major role in risk-taking during financial decisions
  • Makes men selfish and more likely to punish others for being selfish towards them
  • Fatherhood decreases testosterone levels in men, suggesting that the resulting emotional and behavioral changes promote paternal care
  • In animals, higher testosterone levels have been linked to a reduced immune system activity
• Types of male infertility

  • Pretesticular Infertility (Secondary hypogonadism)
  • Testicular Infertility (Primary hypogonadism)
  • Post-testicular Infertility
• Estrogen


  Produced primarily by developing follicles in the ovaries, the corpus luteum, and the placenta. Luteinizing hormone (LH) stimulates the production of estrogen in the ovaries. Some estrogens are also produced in smaller amounts by other tissues such as the liver, adrenal glands, and the breasts. Fat cells also produce estrogen.
• Estrogen synthesis in females

  1. Androstenedione is synthesized from cholesterol in the theca interna cells in the ovary

  2. Androstenedione crosses the basal membrane into the surrounding granulosa cells, where it is converted to estrone or estradiol, either immediately or through testosterone

  3. The conversion of testosterone to estradiol, and of androstenedione to estrone, is catalyzed by the enzyme aromatase
• Estradiol levels


  Vary through the menstrual cycle, with levels highest just before ovulation
• Functions of estrogen


  • Structural: promote formation of female secondary sex characteristics, accelerate metabolism, reduce muscle mass, increase fat stores, stimulate endometrial growth, increase uterine growth, increase vaginal lubrication, thicken the vaginal wall, maintenance of vessel and skin, reduce bone resorption, increase bone formation, morphic change (endomorphic -> mesomorphic -> ectomorphic)
  • Protein synthesis: increase hepatic production of binding proteins
  • Coagulation: increase circulating level of factors 2, 7, 9, 10, plasminogen, decrease antithrombin III, increase platelet adhesiveness
  • Lipid: increase HDL, triglyceride, decrease LDL, fat deposition
  • Fluid balance: salt (sodium) and water retention, increase cortisol, SHBG – sex hormone binding globulin
  • Gastrointestinal tract: reduce bowel motility, increase cholesterol in bile
  • Melanin: increase pheomelanin, reduce eumelanin
  • Cancer: support hormone-sensitive breast cancers
  • Lung function: promotes lung function by supporting alveoli (in rodents but probably in humans)
• Estrone (E1)


  Most abundant estrogen in post menopausal women
• Estradiol (E2)


  Most potent estrogen secreted by the ovary
• Estradiol (E2)


  • Most potent estrogen secreted by the ovary
  • Most abundant estrogen in the pre menopausal women
  • Serves a negative feedback for FSH
  • Used in assessing ovarian function
• Estriol (E3)


  • Metabolite of estradiol
  • The estrogen found in the maternal urine
  • Major estrogen secreted in the placenta
  • Used to assess the fetoplacental unit, post date gestations and intra uterine retardation
  • Used as marker for Down Syndrome (together with AFP and hCG)
• Progesterone


  • Produced in the ovaries, adrenal glands, and during pregnancy, in the placenta
  • Stored in adipose (fat) tissue
  • Used primarily for the evaluation of fertility in female
  • Deficiency results in failure of implantation of embryo
  • Single best hormone to determine whether ovulation has occured
• Progesterone production during pregnancy

  1. Corpus luteum produces it initially, then placenta takes over after 8th week

  2. Placenta utilizes maternal cholesterol as the initial substrate

  3. Placenta produces about 250 mg progesterone per day at term
• Relaxin


  • Produced by corpus luteum of ovary, breast, and placenta during pregnancy
  • In males, enhances motility of sperm
  • In females, peaks within 14 days of ovulation and declines without pregnancy
  • Believed to soften the pubic symphysis during pregnancy
• Gastrin


  Hormone that stimulates secretion of gastric acid (HCl) and aids in gastric motility
• Incretin


  Group of gastrointestinal hormones that cause an increase in insulin release, slow nutrient absorption, and inhibit glucagon release
• Androsterone


  Steroid hormone with weak androgenic activity, made in the liver from metabolism of testosterone
• Medullipin


  Hormone created by renal papilla, converted to medullipin II in the liver, results in vasodilation and decreased blood pressure
• 1. Acylphosphatidylethanolamines (NAPEs)


  Hormones released by small intestine that suppress appetite when processing fat
• Cholecystokinin


  Peptide hormone that stimulates digestion of fat and protein
• Gastric inhibitory polypeptide (GIP)


  Hormone that regulates stomach acid, motility, and secretion
• Motilin


  Hormone that increases gastrointestinal motility and stimulates pepsin production
• Secretin


  Hormone that regulates pH of duodenal contents by controlling gastric acid secretion and bicarbonate release
• Atrial natriuretic peptide (ANP)


  Vasodilator hormone secreted by heart muscle cells in response to high blood pressure, reduces water, sodium, and fat loads on circulation
• Osteocalcin


  Hormone secreted by osteoblasts that regulates metabolism, promotes bone building, and influences insulin and adiponectin
• Leukocyte-promoting Factor


  Cytokine/hormone produced by neutrophils that stimulates bone marrow to increase leukopoiesis
• Erythropoietin


  Glycoprotein hormone that controls red blood cell production
• Urodilarin


  Hormone that causes diuresis by increasing renal blood flow, important in oliguric patients