Primary hyperaldosteronism

Conn syndrome (or primary hyperalderosteronism) is a condition of excess of aldosterone production. This entity is due and occurs secondary to an autonomous solitary adrenal adrenal cortical adenoma in 80% of cases, bilateral adrenal hyperplasia, or rarely, adrenal carcinoma. Excess secretion of aldosterone can also occur in renin-related hypertensionDifferentiation between the causes is required to avoid unnecessary surgery. 

Clinical and laboratary featurespresentation

ItConn syndrome typically presents typically with diastolic hypertension, metabolic alkalosis, and hypokalaemia.

Primary hyperaldosteronism is distinguished from secondary hyperaldosteronism by measurement of serum renin; renin levels are low in the former and high in the latter.

Clinically, Conn's syndrome is characterized by hypertension, muscular Other symptoms include muscular weakness, paresthesias, headache, polyuria, and polydipsia. Oedema is rare in these patients.

Pathology

Primary hyperaldosteronism is distinguished from secondary hyperaldosteronism by measurement of serum renin:

• primary: low renin levels
• secondary: high renin levels

Aetiology

Conn syndrome is due to an autonomous solitary adrenal cortical adenoma in 80% of cases, with the remainder almost entirely due to bilateral adrenal hyperplasia with adrenal carcinoma being a rare cause. 

Excess secretion of aldosterone can also occur in renin-related hypertension. 

Markers

Biochemical analysis may demonstrate hypokalaemia, which may be the first clue to the diagnosis of aldosteronoma in a patient being evaluated for hypertension. The baseline plasma aldosterone is usually greater than 20 g/dL.

Radiological diagnosisRadiographic features

Most aldosteronomas are less than 2 cm in diameter and unilateral in 95% of cases. Assay of aldosterone levels in blood obtained via selective catheterization of both adrenal veins is the most reliable diagnostic procedure. Selective adrenal arteriography, adrenal phlebography, radionuclide studies and CT scans are helpful in diagnosis. Adrenal adenomas in this conditionConn syndrome tend to be quiteunilateral (95%) quite small, often 0.6-1.5~ 2 cm (range 1-5 cm) in diameter, and can be a challenge to detect, even by CT or MR imaging.

CT

On CT,

• aldosteronomas are homogeneous and often hypodense, with an attenuation value near that of water. CT (<10 HU)
• none or minimal contrast enhancement
• rarely calcify
• detects 70% of aldosteronomas, although small lesions may be missed. If
• if CT findings are negative, selective adrenal venous sampling for aldosterone or a dexamethasone suppressed iodocholesterol adrenal scan may identify the lesion

Angiography

Adrenal venous sampling to assay aldosterone serum via selective catheterization of both adrenal veins, may still only be helpful in ~50% of cases.

Treatment and prognosis

If a solitary adrenal mass is detected, surgical adrenalectomy will correct hypertension in 75% 90-90% of cases. Adrenal hyperplasia is the cause in most of the remaining 20% of cases of Conn's syndrome, with adrenal carcinoma occurring rarely. Bilateral adrenalectomy in patients with hyperplasia is not usually an effective treatment and results in adrenal insufficiency and is usually treated medically. Thus differentiation between the causes is required to avoid unnecessary surgery. 

EtymologyHistory and etymology

It is named after J W Conn, who first described the condition in 1955 ⁴.

See also

• adrenal adenoma