FAQ on Adrenal Hormones

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FAQ on Adrenal Hormones:

1. Define the following terms: "corticosteroid," "mineralocorticoid," "glucocorticoid," and "androgen."

Corticosteroid:

A 21-carbon steroid produced in response to ACTH (from pituitary gland), or produced due to release of angiotensin II. This class of steroids influences metabolism. They are used clinically for suppression of ACTH secretion by the anterior pituitary.

Mineralocorticiod:

A type of corticosteroid chiefly influencing the regulation of electrolyte and water balance.

Glucocorticoid:

A type of corticosteroid chiefly influencing carbohydrate, fat and protein metabolism.

Androgen:

A hormone which produces male sexual characteristics.

All the above hormones are produced by the adrenal cortex.

2. List the major functions of the glucocorticoids:

METABOLISM:

1. Permissive activity to facilitate the mobilization of fuels.

2. Gluconeogenesis (protein and fat to glycogen).

3. Lipolysis.

4. Ketogenesis.

5. Powerful antagonism of the actions of insulin on glucose metabolism, inhibiting insulin-stimulated glucose uptake in muscle and adipose tissue and reversing insulin suppression of hepatic glucose production.

MUSCLE:

1. Maintains contractility and work performance of skeletal and cardiac muscles.

2. Increase Ach synthesis in myoneural junctions.

3. Increase myocardial Na+,K+-ATPase and beta-adrenergic receptors.

4. Excess cortisol - decreases muscle protein synthesis, increases muscle catabolism and decrease muscle mass and strength.

BONE:

1. Inhibition of bone formation.

2. Reduction of synthesis of type I collagen.

3. Decrease rate of differentiation of osteoprogenitor cells to osteoblasts.

4. Decreased absorption of calcium from GIT.

5. Antagonize actions of calcitriol, diminish synthesis of calcitriol.

6. Increase rate of bone resorption.

CONNECTIVE TISSUE:

1. Thinning of skin and capillaries by inhibiting collagen synthesis.

2. Increase capillary fragility.

VASCULAR SYSTEM:

1. Required for maintenance of normal blood pressure.

2. Permits normal responsiveness of arterioles to the constrictive action of catecholamines and angiotensin.

3. Decrease production of vasodilator prostaglandins.

4. Decrease permeability of vascular endothelium.

KIDNEYS:

1. Increase glomerular filtration rate.

2. Increase glomerular plasma flow.

3. Decrease preglomerular resistance.

4. Increase ammonium ion generation from glutamate in response to acid load.

5. Increase phosphate excretion by decreasing reabsorption from.

PCT:

1. Increase sodium retention and potassium excretion.

FETUS:

1. Cortisol facilitates in utero maturation of the CNS, retina, skin, GIT and lungs.

CNS:

1. Modulation of excitability, behavior, sleep and mood.

2. Salty taste and other sensory stimuli are dampened.

3. Improves ability to integrate sensations that are perceived and organize appropriate responses.

INFLAMMATORY and IMMUNE RESPONSES:

1. Inhibition of reactions that are normally activated by inflammation.

2. Suppression of the immune system responses to foreign substances, hence its use in prevention of rejection of transplanted tissue of non-self origin.

*Cortisol is essential to the survival of the severely stressed, traumatized or infected individual.

3. What are the effects of cortisol on blood glucose? How is this effect mediated?

• Low blood levels of glucocorticoids, mainly cortisol, stimulate neurosecretory cells in the hypothalamus to secrete corticotroin-releasing hormone, CRH, which promotes release of ACTH from anterior pituitary.

• ACTH flows in the blood to adrenal cortex, stimulating glucocorticoid secretion, and raising blood glucose.

• The effect is mediated by receptors (neurosecretory cells in the hypothalamus), corticotrophs in the anterior pituitary, and effectors (cells of zona fasciculata).

4. What do we mean by the "permissive actions" of cortisol?

Cortisol works with other steroids to reinforce their actions.

5. Describe the functions of aldosterone:

• Stimulates active sodium reabsorption in the renal tubules.

• Stimulates active potassium secretion in renal tubules.

6. Why are aldosterone-blocking drugs administered to control hypertension?

Aldosterone works by retaining Na secretion through the kidneys, hence, increasing blood pressure. If the action of aldosterone is blocked, Na would be secreted by the kidneys, hence, lowering blood pressure.

7. A patient secretes an excess of cortisol but normal amounts of aldosterone. Will his blood pressure be affected? Explain.

Excess cortisol would cause higher than normal blood glucose, which further causes high BP. If the aldosterone levels are normal, the patient would become hypertense.

8. What are the functions of the sex hormones produced in the adrenal cortex?

Assist in development of secondary sexual characteristics; axillary and pubic hair, contribute to libido and are a source of estrogens after menopause.

9. How important is the adrenal cortex in the production of androgens in a normal man? A normal woman?

In both males and females, the adrenal cortex secretes androgens. The major androgen secreted is dehydroepiandrosterone (DHEA). Androgen secretion is stimulated by ACTH.

Additional Readings:

Basic Endocrinology

1. Introduction to Endocrinology
2. Hypothalamic-pituitary system
3. Adrenal Hormones
4. Antidiuretic Hormone (ADH) and ECF Regulation
5. Endocrine Pancreas
6. Growth Hormone
7. Adrenal Medulla
8. Hormonal Control of Calcium and Phosphate
9. Thyroid Hormones
10. Hormones of Male Reproduction
11. Hormones of Female Reproduction
12. Fluid Compartments of the Body
13. Notes on Hypothalamus Anterior Pituitary and Thyroid
14. Additional Notes on Female Reproduction
15. Hormonal Signaling Pathways
16. FAQ on Adrenal Hormones
17. FAQ on Male Reproduction
18. Synthesis and Deficiencies of Adrenal Hormones
19. Significance of Glycosylated Hemoblogin (HbA1c)
20. Significance of Measuring Albumin while with Calcium Levels
21. Stepwise Approach to Treatment of Ascites
22. How to differentiate between Diabetes Insipidus vs Psychogenic Polydipsia

Related Topics

1. Histology of the Endocrine System
2. Histology of the Male Reproductive System
3. Histology of the Female Reproductive System

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