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13 Cards in this Set

  • Front
  • Back
Name the five classes of steroid hormones
Glucocorticoids - Cortisol promotes glucogenesis, supresses immune, inflammation and allergic responses.
Mineralocorticoids - Aldosterone maintains electrolyte balance
Androgens - Testosterone stimulates spermatogenesis, protmotes development of male secondary sex characteristics, promotes anabolism, masculinization of fetus
Estrogens - control menstrual cycle, promote development of female secondary sex characteristics
Progestins - Progesterone conrols secretory phase of uterus and mammary glands, impolantation and maturation of fertilized ovum
Discuss steroid hormone synthesis related to STAR and desmolase (CYP11A)
1. Transport of cholesterol into the mitochondrion view the steroid acute regulatory (StAR) protein.
2. Removal of the hydrocarbon side chain of cholesterol by CYPIIA (desmolayse) RATE LIMITING
3. Movement of metabolic intermediates between mitochondrion and ER for further modification
4. Branch point for cortisol & aldosterone synthesis or cortisol and DHEA synthesis.

Desmolase also produces pregnenolone, which is returned to the cytosol for an oxidation reaction that involves a 3-β-hydroxysteroid dehydrogenase followed by an isomerisation reaction producing progesterone, an intermediate in the syntheses of aldosterone and cortisol.
Describe the steroid hormones synthesized and released from the adrenal cortex
Zona Fasciculata - Cortisol
Zona Glomeruloa - Cortisol, Aldosterone, DHEA
Zona Reticularis - DHEA
Indicate the synthesis and the metabolic actions of cortisol
Synthesis - controlled by pituitary gland
1. Hypothalus makes corticotrophin releasing hormone (CRH)
2. Promotes anterior pituitary to make adrenocorticotrophic hormone (ACTH)
3. Promotes cortisol synthesis which inhibits the other two organs.
Indicate the synthesis and the metabolic actions of aldosterone
Aldosterone stimulates renal reabsorption of Na+ and excretion of K+
Indicate the synthesis of DHEA and testosterone in the adrenal cortex
DHEA is the precursor for androstenedione (weak)
Once secreted it is converted to testosterone and estradiol (strong)
Testosterone produced in testis (trace amt in adrenal)
Describe the synthesis of testosterone in the testes
• Leutinizing hormone stimulates androgen synthesis in the Leydig cells of the testes.
• production is through pregnenolone to DHEA, a reaction catabolised by CYP17.
• DHEA is further metabolized to androstenedione by a 3-β-hydroxy steroid dehydrogenase.
• Androstenedione undergoes reduction to form testosterone which is secreted into the blood.
Discuss congenital adrenal hyperplasias (CAH) and describe clinical features and biochemical basis of manifestations in patients with CYP 21 and CYP 11B and CYP 17 deficiencies
Memorize Lippincott figure 18.25 - steroid hormone synthesis
Indicate the hormone abnormality in Cushings’ and Addison’s disease
Cushing's Disease - oversecretion of cortisol resulting from prolonged exposure to high amounts of glucocorticoids.
- hyperglycaemia, muscle wastage, thin limbs, buffalo hump and moon face, premature ischaemic heart disease, hypertension, hypokalaemia

Addison's Disease - primary hypoadrenalism with destruction of the entire adrenal cortex and an inability to produce either glucocorticoids or mineralcorticoids
Symptoms - fever, abdominal pain, pigementation & hypotensive collapse
- autoimmune attack and occassionally TB.
- Low aldosterone - hyponatraemia (high Na+ in urine), hyperkalaemia
- Low cortisol - hypglycemia, hypotension (low Na+ in serum)
Indicate the biochemical basis for the occurrence of hyperglycemia in Cushing’s syndrome
Cortisol enhances epinephrine's effects including its suppression of insulin, leading to hyperglycemia.
Describe the synthesis of estradiol in the ovaries
• Oestrogens are primarily produced in the ovarian follicle and corpus luteum, in response the follicle stimulating hormone (FSH).
• FSH stimulates the P450 aromatase enzyme of the ovarian granulosa cells to convert testosterone into oestradiol.
• Androstenedione can also be converted to estrone in the ovaries as well as extraovarian tissue
• Androstenedione (weak) is also produced in the adrenal cortex and is responsible for androgenic (masculinising) effects in females.
• In males, oestrogen production is minimal is produced by the microsomal enzyme P450 aromatase.
• Only very small amounts of oestradiol are produced in the testes, remainder being produced in the adipose tissues, skin, liver and brain.
Where does the synthesis of sex hormones branch?
DHEA and Adrostenedione made in adrenal gland
Oestrone, Testosterone and Oestradiol made in gonads