Hypertension is a common medical disorder in pregnancy that may predate or first appear in pregnancy. Endocrine causes of hypertension are rare in pregnancy. However, it is imperative to have a high index of suspicion because they carry much higher foetal and maternal morbidity and mortality risks. Endocrine disorders presenting as hypertension are primarily the result of autonomous production of renin, aldosterone, cortisol, or catecholamines.
Cushing's syndrome is distinctively rare in pregnancy because fertility is generally reduced due to abnormal gonadotrophin secretion. In pregnancy adrenal adenoma is the most common cause of Cushing’s syndrome followed by Cushing’s disease.
The diagnosis of Cushing’s syndrome during pregnancy may pose a challenge because of overlapping clinical and biochemical features with normal pregnancy. Useful differentiating features may include muscular weakness, purple striae, and osteoporosis - the more catabolic features of Cushing’s syndrome and psychiatric disturbance. Normal circadian rhythm of cortisol secretion is loss in all forms of Cushing’s syndrome therefore midnight plasma cortisol level and late-night salivary cortisol may be useful; however the diagnostic thresholds in pregnancy have not been determined. Urinary free cortisol can only be relied upon if it is more than three times the upper range of normal, particularly in the second and third trimesters. Surgery is more effective, but if no possible medical treatment with metyrapone can be considered.
Pheochromocytoma is rare but potentially fatal. Early recognition is important as there are high rates of maternal and foetal complications if undiagnosed. Catecholamine production generally remains stable during pregnancy; only slightly elevated even in pre-eclampsia. First-line investigation include measurement of plasma or 24-hour urinary fractionated metaneprhines. Adrenalectomy should only be attempted after optimization of medical therapy with α-adrenergic receptor blockade followed by beta blockade.
Primary hyperaldosteronism is rare despite hypertensive disorders affecting 6-8% of all pregnant women and primary hyperaldosteronism being assumed to account for 10% of all hypertensive disorders. It is likely that primary hyperaldosteronism is significantly underestimated in the pregnant population due to the difficult diagnosis. There are no validated reference ranges for aldosterone and renin during gestation, however a suppressed plasma renin activity and elevated aldosterone is suggestive of the diagnosis.
Surgery can be performed in second trimester if there was a unilateral adenoma, otherwise defer investigation and definitive treatment until after delivery. Optimal BP control, often achieved medically, is the most important factor in predicting pregnancy outcomes