Download 13.10: Physiological Roles of Steroid Hormones

13.10: Physiological Roles of Steroid
Hormones
Sierra Barnhart
And
Chelsalyn Corcoran
Synthesis of Steroid Hormones
 Cholesterol is starting material for synthesis of Steroid
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Hormones.
Aliphatic side chain on the D ring is shortened.
Six Carbon unit is removed.
Secondary alcohol group on 3rd 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:
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+
1.
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 PGG₂
 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 PGH₂
 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