Sierra Barnhart And Chelsalyn Corcoran 13.10: Physiological Roles of Steroid Hormones

Synthesis of Steroid Hormones Cholesterol is starting material for synthesis of Steroid Hormones. Aliphatic side chain on the D ring is shortened. Six Carbon unit is removed. Secondary alcohol group on 3 rd carbon is oxidized to a ketone. Progesterone is produced. Progesterone- starting compound for the sex hormones and adrenocorticoid hormones.

Adrenocorticoid Hormones Products of the adrenal glands. Classified in groups by function: 1. Mineralocorticoids-regulate concentration of ions. 2. Glucocorticoids- Control carbohydrate metabolism. Corticoid- means site of secretion is the outer part of the gland. Aldosterone- one of most important mineralocorticoids. Increased secretion enhances the re-absorption of Na+ and Cl- ions in kidney tubules. Increase the loss of K+

Continued…. Na+ concentration controls water retention in tissues. Controls tissue swelling. Cortisol- major glucocorticoid. Increase glucose and glycogen concentration. Fatty acids from body proteins are transported to liver, cortisol manufactures glucose and glycogen. Ketone derivative. Anti-inflammatory. Synthetic derivatives used for inflammatory diseases of organs: Bronchial asthma, rheumatoid arthritis

Sex Hormones Testosterone- most important male sex hormone Promotes normal growth of genital organs During puberty: testosterone production is increased Causes deep voice, facial and body hair Most important female sex hormone- estradiol Synthesized from testosterone by aromatization of A ring.

Continued… Estradiol and progesterone regulate menstrual cycle. Beginning of cycle: estradiol rises causing the uterus lining to thicken. The luteinizing hormone triggers ovulation. If ovum is fertilized, progesterone will inhibit ovulation. Estradiol and progesterone prepare the uterine lining to receive the fertilized ovum.

Continued… If no fertilization: progesterone stops and estradiol decreases. Causes the uterine lining to thin down, and menstrual bleeding occurs Blocking progesterone terminates a pregnancy Progesterone interacts with a receptor in the nucleus of cells. Receptor then changes its shape.

Mifepristone Mifepristone also called RU486 acts as a competitor to progesterone. Blocks the action of progesterone by binding to the same receptor cites. Progesterone molecule can’t reach the receptor molecule so uterus isn’t prepared for implantation and ovum is aborted. After pregnancy is established, RU486 will be taken up through 49 days of gestation.

Continued… Supplement to surgical abortion. Binds to the receptors of glucocorticoid hormones too Used as an antiglucocorticoid. Also recommended to alleviate Cushing syndrome (overproduction of cortisone) Morning after pill is different: Can be taken up to 72 hours after unprotected intercourse Acts before the pregnancy takes place

2 kinds on the market as prescription drugs: Levonogestrel- progesterone- like compound Preven- combination of levonogestrel and ethynil estradiol Estradiol and progesterone regulate secondary female sex characteristics. RU486 used as an antiprogesterone can prevent certain types of breast cancer.

Male and Female Sex Hormones Testosterone and estradiol are not exclusive to males or females. A small amount of estradiol is produced in males Small amount of testosterone in females Only when hormonal balance becomes upset, can one have symptoms of abnormal sexual differentiation.

13.11 What Are Bile Salts? Oxidation products of cholesterol Cholesterol is oxidized to the trihydroxy derivative The end of the aliphatic chain is oxidized to the carboxylic acid. The latter forms an amide bond with an amino acid.

Bile salts are powerful detergents One end of the molecule is hydrophilic, due to its negative charge, and the rest is hydrophobic Can spread dietary lipids in the small intestine into emulsions, facilitating digestion. Similar to soap on dirt

Eliminated in feces Remove extra cholesterol Eliminated through bile salts Solubilize deposited cholesterol in the form of cholesterol particles

13.12 What are Prostaglandins, Thromboxanes, and Leukotrienes? Prostaglandins 1930s Kurzrok andLeib Demonstrated semi fluid causes a hysterectomized uterus to contract Ulf von Euler isolated the compounds from semen Thought they came from prostate glad, thus prostaglandin

Seminal gland secretes 0.1 mg/ day in matured men Small amounts present in both male and female Synthesized from arachidonic acid by ring closure at carbons 8 and 12 Cyclooxygenase (COX) catalyzes reaction Product is PGG ₂ Persecutor of PGE PGF

E group has carbonyl group on carbon number 9 Subscript represents number of double ponds in the hydrocarbon chain F group – two hydroxyl groups on ring at 9 and 11

Cyclooxygenase Two forms: COX-1: catalyzes physiological production of prostaglandins (always present add more) COX-2: responsible for prostaglandins in inflammation

Thromboxanes Class of arachidonic acid derivatives is thromboxanes Ring closure Deived from PGH ₂ Ring is cyclic acetal Induces platelet aggregation

Leukotrienes Act to meditate hormonal responses Derived from arachidonic acid No ring closure

Occur mostly in white blood cells Found in body tissue Create long-lasting muscle contractions Stronger than histamines

Cause fever and inflammation Inhibiting uptake by leukotriene receptors stops effects Zafirlukast helps to control chronic asthma