WEEK 3: Adrenal physiology

Question 1

The adrenal medulla produces catecholamines. State 3 examples of catecholamines.

Answer 1

Dopamine
Norepinephrine
Epinephrine (also known as adrenalin or adrenaline

Question 2

Give examples of androgens produced by the zona reticularis of the adrenal cortex and state their functions.

Answer 2

1. Dehydroepiandrosterone (DHEA): It is the most abundant androgen in circulation. DHEA serves as a precursor for the synthesis of other androgens, such as testosterone and dihydrotestosterone (DHT), which play crucial roles in the development of male secondary sexual characteristics, including the growth of facial and body hair, deepening of the voice, and maintenance of muscle mass and bone density.
2. Androstenedione: It is another precursor for testosterone and estrone synthesis. While its direct effects are relatively weak compared to testosterone, androstenedione contributes to overall androgen levels in the body and can be converted to testosterone in peripheral tissues. Testosterone is essential for the development of male reproductive organs, spermatogenesis, and libido.

Question 3

Give examples of glucocorticoids produced by the zona fasciculata of the adrenal cortex and state their functions.

Answer 3

1. Cortisol (Hydrocortisone):
   *Cortisol plays a crucial role in regulating metabolism by promoting gluconeogenesis (the synthesis of glucose from non-carbohydrate sources) in the liver. This helps increase blood glucose levels, providing energy during times of stress or fasting.

*Cortisol also has anti-inflammatory effects by inhibiting the immune response, reducing the production of inflammatory mediators, and suppressing the activity of immune cells.

*Additionally, cortisol modulates mood, cognition, and the sleep-wake cycle, and it helps regulate blood pressure.

2. Synthetic Glucocorticoids (e.g., Prednisone, Dexamethasone): These are commonly used in medicine for their potent anti-inflammatory and immunosuppressive effects.

MOA
1. PREDNISONE
2. DEXAMETHASONE

Question 4

State examples of mineralocorticoids produced by the zona glomerulosa of the adrenal cortex and state their functions.

Answer 4

Aldosterone:
This is the principal mineralocorticoid produced by the adrenal cortex.

Aldosterone acts on the kidneys to increase sodium reabsorption and potassium excretion, thereby regulating blood volume and blood pressure.

It also indirectly affects water retention, helping to maintain electrolyte balance and blood pressure within normal ranges.

Question 5

Discuss the Synthesis of steroid hormones

Answer 5

1. Cholesterol&raquo_space;> Progesterone
   *Progesterone acted on by DHEA&raquo_space;> Testosterone&raquo_space;> estradiol
   *Progesterone»> Cortisol
   *Progesterone&raquo_space;> Aldosterone

Prednisone and Dexamethasone are drugs that look like cortisol and have anti-inflammatory effects in the body just like cortisol.

Question 6

Q: What proportion of the adrenal cortex does the Zona glomerulosa constitute?

Q: What hormones are secreted from the Zona glomerulosa of the adrenal cortex?

Answer 6

A: The Zona glomerulosa constitutes approximately 15% of the adrenal cortex.

A: The Zona glomerulosa primarily secretes mineralocorticoids, with aldosterone being the major hormone.

Question 7

Q: How do cortisol, corticosterone, and cortisone contribute to mineralocorticoid activity?

Answer 7

A: While primarily glucocorticoids, cortisol, corticosterone, and cortisone can exert slight mineralocorticoid effects, particularly when present in high concentrations or when other regulatory mechanisms are disrupted.

Question 7

Q: Which hormone accounts for about 90% of the mineralocorticoids secreted by the adrenal cortex?

Q: Name the enzyme essential for the synthesis of aldosterone in the adrenal cortex.

Answer 7

A: Aldosterone is the major mineralocorticoid hormone secreted by the adrenal cortex, constituting about 90% of the total mineralocorticoid output.

A: Aldosterone synthase is an enzyme essential for the synthesis of aldosterone in the adrenal cortex.

Question 7

Outline major stimuli for regulation of aldosterone secretion. (4)

Answer 7

Major stimuli
*Raised extracellular K+: hypokalemia
*Increased angiotensin II activity
*Reduced extracellular Na+: hypernatremia
* ACTH increase secretion

Question 8

Describe the Regulation of aldosterone secretion

Answer 8

RAAS system

1. Stimuli for Renin release
   *Reduced sodium delivery to the distal convoluted tubule detected by macula densa cells.
   *Reduced perfusion pressure in the kidney detected by baroreceptors in the afferent arteriole.
   *Sympathetic stimulation of the JGA via β 1 adrenoreceptors.

NOTE: The other name for angiotensinogen= a2 Globulin

Question 9

Discuss Mineralocorticoids: Aldosterone physiological functions