Essential (primary) hypertension, which is high blood pressure of unknown cause, generally develops in the middle years. The onset of hypertension in the teenage years or after the age of sixty, therefore, should raise a question about its underlying cause. Could the elevated blood pressure be secondary to kidney (renal) disease, a disruption in the blood circulation to the kidneys (renal artery blockage), or an adrenal gland hormone abnormality?
I recently saw a healthy appearing, athletic teenage boy in consultation. He had developed the recent onset of hypertension to as high as 180/110. The normal blood pressure in this age group is well under 140/90. Because of his young age, this patient had already had what was thought to be a complete medical workup to diagnose or exclude (rule out) the secondary causes of hypertension. He had also had a heart evaluation. In fact, an ultrasound exam of his heart (echocardiography) showed no enlargement yet from the hypertension.
A screening test using radioisotope imaging to detect a blockage of his renal arteries was normal (negative). This test is about 90% effective in ruling out a significant blockage that could stimulate the renin-angiotensin-aldosterone hormonal system to raise the blood pressure. Additionally, an excess of adrenalin was eliminated as a potential cause of the hypertension by the finding of normal urine hormone assays for catecholamines. The catecholamines are the metabolic products of adrenalin-related compounds.
As a result of a urine test, it was determined that the youngster had evidence of renal damage. This was shown by the leakage of protein in the urine (proteinuria). The discovery of the renal damage, however, did not help in the investigation because kidney disease can either be the cause or the result of hypertension. Accordingly, with the thought that the boy might have primary renal disease causing the hypertension, a renal tissue sampling (biopsy) was performed. It turned out, however, that the biopsy showed nephrosclerosis, which is renal damage that is caused by hypertension. Therefore, the investigation for a cause of his hypertension continued.
Further hormone tests revealed a low renin level and a borderline aldosterone level. This combination suggested that he had excessive amount of salt retaining hormone in his body, which could contribute to hypertension by causing salt retention. Magnetic resonance imaging (MRI) of his adrenal glands, however, showed no evidence of an adrenal tumor that could produce and secrete the excess salt-retaining hormone. From where, then, could this salt-retaining hormone be coming?
Recent studies have revealed genetic (inherited) defects that can cause adrenal gland secretion of excessive salt-retaining hormones that can cause hypertension. As a matter of fact, the boy's fraternal grandfather also had hypertension starting at a young age. Not yet willing to accept that this teenager had essential hypertension, we had genetic studies performed at Brigham and Women's Hospital in Boston. Indeed, he was found to have the gene for Glucocorticoid-remediable Aldosteronism (GRA), which is an unusual and not widely recognized form of hypertension that is caused by a genetic abnormality. This abnormality ultimately makes the adrenal gland produce excess aldosterone, which causes the hypertension. Although, as the name implies, GRA can be treated with glucocorticoid (cortisone), other medications currently are thought to be preferable. We subsequently learned that two of his teenage cousins on his father's side also have hypertension, and probably have the same genetic disturbance in their adrenal hormone production.
Making the diagnosis of GRA was very critical for this youth for several reasons. For one, certain specific types of medications directed at his salt-retaining hormone abnormality will provide the best treatment for him. Furthermore, he will need to be watched for the occurrence of intra-cranial aneurysms (dilated or widened arteries in the head) that may develop during his life. These aneurysms can burst and bleed, often with catastrophic results. Accordingly, the aneurysms need to be detected early so that they can be treated surgically in a preventive fashion before they ever bleed. Finally, if he has children, they would have a 50% chance of inheriting this same gene and developing hypertension.
Genes, those amazing parts of chromosomes that determine the characteristics of individuals, are becoming increasingly important in many areas of medicine. Thus, as we learn more about genetic factors in hypertension, we are likely to identify other genes that contribute to the development of high blood pressure. Moreover, genetic factors will probably play a future role in the type and dosage of medications that we use to treat hypertension in certain sub-groups of patients.
Medical Author: Dwight Makoff, M.D.
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