Adrenal Gland Disorders

It is the innermost part of the adrenal gland, consisting of chromaffin cells that secrete catecholamines, including epinephrine (adrenaline), norepinephrine (noradrenaline), and a small amount of dopamine, in response to stimulation by sympathetic preganglionic neurons.

Reference: Davidson 23rd; P-668

Reference: Davidson 23rd; P-665

Hyperkalaemia is a common finding in adrenal insufficiency due to decreased aldosterone secretion. Davidson explains that oestrogen normally promotes sodium reabsorption and potassium excretion in the kidneys. In Addison’s disease, low aldosterone levels lead to sodium loss and potassium retention. Harrison adds that adrenal insufficiency also leads to hyponatremia and volume depletion due to salt wasting.

Osteoporosis is a well-known side effect of long-term corticosteroid therapy. Davidson explains that corticosteroids reduce bone formation and increase bone resorption, leading to decreased bone density and an increased risk of fractures. Harrison adds that patients on long-term corticosteroids should be monitored for bone loss and may require prophylactic treatment with calcium, vitamin D, and bisphosphonates to reduce the risk of osteoporosis.

Explanation: Features of an acute adrenal crisis include circulatory shock with severe hypotension, hyponatraemia, hyperkalaemia and, in some instances, hypoglycaemia and hypercalcaemia.

The low-dose dexamethasone suppression test is the best screening test for Cushing’s syndrome. Davidson explains that in Cushing’s syndrome, cortisol secretion fails to be suppressed by dexamethasone, indicating autonomous cortisol production. Harrison adds that a 24-hour urine cortisol measurement can also be used to confirm the diagnosis, but the dexamethasone suppression test is more sensitive for detecting mild hypercortisolism.

Reference: Davidson 23rd; P-674

Weight loss with low grade evening fever, cough and night sweats indicates tuberculosis.
Weight loss in spite of good appetite or high food intake—thyrotoxicosis, diabetes mellitus, malabsorption syndrome.
Weight loss with pigmentation and hypotension—Addison’s disease.

Reference: Davidson 23rd; P-676

Reference: Davidson 23rd; P-666

Stem Breakdown:

Episodic headaches, palpitations, and sweating: These are the classic "triad" of symptoms for pheochromocytoma, a catecholamine-secreting tumor.
Consistently elevated blood pressure: Pheochromocytoma often causes paroxysmal or sustained hypertension.
Increased metanephrines and normetanephrines in urine: These are metabolites of catecholamines and are diagnostic for pheochromocytoma.
Option Analysis:

A) Hyperthyroidism: Hyperthyroidism can cause palpitations and sweating, but it typically does not cause paroxysmal hypertension or elevated metanephrines.
B) Pheochromocytoma: This is the correct diagnosis. Davidson and Harrison explain that pheochromocytoma is a rare adrenal tumor that secretes excess catecholamines (epinephrine and norepinephrine), leading to episodic symptoms of headache, palpitations, sweating, and hypertension. Elevated urine or plasma metanephrines confirm the diagnosis.
C) Primary hyperaldosteronism: Primary hyperaldosteronism (Conn’s syndrome) causes hypertension and hypokalemia due to excess aldosterone, but it does not cause episodic symptoms or elevated catecholamine metabolites.
D) Cushing’s syndrome: Cushing’s syndrome can cause hypertension due to excess cortisol, but it is associated with other features such as weight gain, moon face, and purple striae. It also does not cause elevated metanephrines.