BOF:
10
A fifty-year-old patient
attending the hypertension clinic has refractory hypertension. Random
aldosterone: plasma renin activity has shown a ratio of greater than 750. In
order to differentiate the underlying cause of primary aldosteronism,
demonstrated in this patient, you arrange for the patient to have aldosterone:
plasma renin activity measured in the morning (at 8 a.m.) with the patient in
the supine position and again at noon with the patient in the erect position.
This test helps to differentiate the causes of primary hyperaldosteronism
because
a) ACTH
suppresses aldosterone secretion in adrenal adenoma
b) ACTH
has no effect on glucocorticoid suppressible hyperaldosteronism
c) Erect
posture increases plasma aldosterone in adrenal hyperplasia
d) ACTH
levels are higher at noon
e) The
supine position increases aldosterone secretion in glucocorticoid suppressible
hyperaldosteronism.
Answer:
c)
In primary aldosteronism, the aldosterone: PRA (plasma
renin activity) ratio is greater than 750.
The causes of primary aldosteronism are
·
An aldosterone producing adenoma (Conn's syndrome)
·
Bilateral adrenal hyperplasia
·
Glucocorticoid suppressible hyperaldosteronism
·
Adrenal carcinoma (rare)
·
Unilateral hyperplasia (rare)
By measuring aldosterone: PRA ratio at 8a.m. in the supine position and at noon
in the erect position one may differentiate between these conditions.
Posture has an effect on aldosterone levels in adrenal hyperplasia.
Erect posture increases plasma aldosterone.
ACTH produces a marked effect in patients with glucocorticoid suppressible
hyperaldosteronism.
It increases aldosterone levels.
ACTH has no effect in adrenal hyperplasia
ACTH has only a small effect on adrenal adenoma
At 8a.m. ACTH levels are higher than at noon.
