Biology of Disease

individuals are treated with cortisol and, if necessary, aldosterone. The
treatment should reduce ACTH secretion and therefore excessive androgen
production. The treatment requires monitoring by regular measurements of
plasma 17A-hydroxyprogesterone.

Conn’s Syndrome

Conn’s syndrome, also called primary hyperaldosteronism, is characterized by
an increased production of aldosterone. In 80% of cases this is due to an adrenal
adenoma. Other causes include hypertrophy of the zona glomerulosa of the
adrenal cortex and adrenal carcinoma, although the latter is extremely rare.
The excessive secretion of aldosterone leads to the increased retention of Na+
and loss of K+ by the kidneys. Most of the clinical features, muscle weakness,
tetany, paresthesiae, polydipsia and polyuria, are due to the hypokalemia
(Chapter 8) whereas the excessive Na+ retention causes hypertension.

Diagnosis and treatment of Conn’s syndrome

Investigating the possibility of Conn’s syndrome involves determining the
concentrations of Na+ and K+ in the serum and urine of the patient. Plasma
Na+ can be high, slightly increased or normal, whereas that of K+ is always
reduced. Measurements of plasma aldosterone and renin in patients with
Conn’s syndrome often show a high aldosterone concentration and a low
renin activity. Conn’s syndrome is managed by treating its underlying cause.
Often this is a tumor that must be removed surgically. Other approaches
involve using diuretics, such as spironolactone, an antagonist to aldosterone
that helps to control hypertension. This is particularly useful when the cause
of Conn’s syndrome is adrenal hyperplasia.

DISORDERS OF THE ADRENAL CORTEX

CZhhVg6]bZY!BVjgZZc9Vlhdc!8]g^hHb^i]:YLddY &-,

Cholesterol

Pregnenolone

Progesterone

11-Deoxycorticosterone

Corticosterone

18-Hydroxycorticosterone

Aldosterone

17 A-Hydroxypregnenolone

17 A-Hydroxyprogesterone

11-Deoxycortisol

Cortisol

3 B-Hydroxydehydrogenase,

$5-isomerase

21-Hydroxylase

11 B-Hydroxylase^11 B-Hydroxylase

18-Hydroxylase

17 A-Hydroxylase

17 A-Hydroxylase

3 B-Hydroxydehydrogenase,

$5-isomerase

21-Hydroxylase

Figure 7.32 The synthesis of cortisol and

aldosterone.