Endocrine Abstracts

Background: Primary aldosteronism (PA) is the most frequent cause of hormonal hypertension, typically associated with hypokalaemia. Whereas hypertension with no hypokalaemia can be present in even half of cases, hypokaleamia in normotensive patients is a very rare finding. Mechanisms that act against developing hypertension despite aldosterone excess are at least a few. Some patients with previous low blood pressure increase its values because of hyperaldosteronism, thus still maintaining them in the upper part of the normal range. When screening patients with normotension, other than antihypertensive drugs can interfere with renin–angiotensin–aldosterone system and thus alter biochemical results, with oral anticontraceptives amongst them.

Case description: 34-year-old female, more than a year postpartum, was referred to Endocrinology Department because of refractory hypokalaemia of unknown origin. Kalium concentrations as low as 2.8 mmol/l were observed. Her blood pressure was within the normal range. Because of her gastric disturbances, she had her abdomen CT already performed and left adrenal incidentaloma of 15×20 mm in diameter and density of (–)20 Hounsfield Units was found. She was taking oral contraceptive minipill – desogestrel. Serum aldosterone and direct renin measurements were 11.5 ng/dl and 2.86 µIU/ml [AARR = 4.02 (cut-off level <3.7)], pointing to the possibility of primary aldosteronism. After 6 weeks of withdrawal of desogestrel, repeated screening and saline infusion test results were consistent with PA diagnosis. To assess lateralization of aldosterone production the patient underwent norcholesterol scintigraphy, because of poor availability of adrenal venous sampling and our good experience. Although the image was non-specific, the patient underwent left adrenalectomy without additional testing. Serum aldosterone, direct renin levels and kalaemia returned to normal.

Conclusions: Even in the absence of hypertension, isolated hypokalaemia itself should prompt screening for autonomous aldosterone secretion. In women of reproductive age, progestin-containing drugs can alter other hormone levels and that should be taken into account if biochemical testing is performed.