MEDI7111 Lecture Notes - Lecture 8: Multiple Endocrine Neoplasia Type 2, Headache, Small-Cell Carcinoma
Endocrine 8
Adrenal Hypersecretion Disorders
Conn’s Syndrome/Primary Aldosteronism
Primary aldosteronism occurs in 5-10% of patients with hypertension and should always be
considered as a potentially cause of hypertension.
Pathophysiology
The condition occurs through overproduction of aldosterone either through hyperplasia
(bilateral adrenal hyperplasia) or neoplasia (aldosterone producing adenoma) of the zona
glomerulosa of the adrenal gland. Aldosterone acts to increase potassium excretion and salt
retention, leading to hypokalaemia, hypertension and suppression of renin.
Pathological Process of Primary Aldosteronism Gross Image
Investigations
Primary aldosteronism is diagnosed through biochemistry. An increased aldosterone:renin
ratio +/- low serum potassium may be indicative of the disease. This test has many other
factors which can produce false positives or false negatives, such as medications which
block or upregulate the production or renin or aldosterone, as well as various renal
conditions. Confirmation of the diagnosis is made by fludrocortisone suppression test or
seated saline suppression test.
Once the diagnosis is confirmed, the location (i.e. unilateral or bilateral) and subtype of the
disease needs to be uncovered to determine management. Adrenal CT and venous sampling
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is undertaken to determine if there is bilateral or unilateral involvement, as well as a
genetic test for the FH-1 gene (a rare familial variant of PA).
Management
If disease is unilateral, adrenalectomy is indicated. If the disease is bilateral or the patient is
unsuitable for/doesn’t want surgery, medical therapy is indicated. The goals of medical
therapy are to correct the hypokalaemia, restore normal BP and prevention/reversal of
hyperaldosteronism on heart and lungs. This is done through prescription of aldosterone
receptor antagonists (e.g. spironolactone) and potassium sparing diuretics (e.g. amiloride)
to block the renal effects of aldosterone.
Cushing’s Syndrome
Cushing’s syndrome is a constellation of clinical abnormalities caused by chronically
elevated cortisol. Hypersecretion of cortisol from the adrenal gland can be ACTH dependent
or independent:
ACTH Dependent
oHypersecretion of ACTH by pituitary adenoma (true Cushing’s disease)
oSecretion of ACTH by a non-pituitary tumour – usually small cell lung cancer
(ectopic ACTH)
ACTH Independent
oTherapeutic administration of corticosteroids
oCortisol producing adrenal adenomas/carcinomas
Clinical Features
Diagnosis
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Document Summary
Primary aldosteronism occurs in 5-10% of patients with hypertension and should always be considered as a potentially cause of hypertension. The condition occurs through overproduction of aldosterone either through hyperplasia (bilateral adrenal hyperplasia) or neoplasia (aldosterone producing adenoma) of the zona glomerulosa of the adrenal gland. Aldosterone acts to increase potassium excretion and salt retention, leading to hypokalaemia, hypertension and suppression of renin. An increased aldosterone:renin ratio +/- low serum potassium may be indicative of the disease. This test has many other factors which can produce false positives or false negatives, such as medications which block or upregulate the production or renin or aldosterone, as well as various renal conditions. Confirmation of the diagnosis is made by fludrocortisone suppression test or seated saline suppression test. Once the diagnosis is confirmed, the location (i. e. unilateral or bilateral) and subtype of the disease needs to be uncovered to determine management.
