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my personal edition > hypertension > news
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DGReview
Insulin Resistance May Be a Common Cause of Treatment-Resistant Hypertension
A DGReview of :"High prevalence of secondary hypertension and insulin resistance in patients with refractory hypertension"
Blood Pressure
08/07/2003
By Emma Hitt, PhD
In patients with hypertension, treatment resistance without a clear cause may be frequently associated with insulin resistance, according to new research.
Prevalence of refractory hypertension ranges from 3% in primary care to 13% in referral centers, according to Nieves Martell, MD, with the Unidad de Hipertension, Hospital Clínico San Carlos, Madrid, Spain, and colleagues.
"To diagnose a patient as truly resistant to therapy, it is necessary to exclude several causes of resistance including non-compliance, suboptimal medical regimen, interfering substances or drugs, pseudo hypertension, white coat effect and secondary hypertension," they write.
For patients in whom hypertension is not clearly secondary, treatment resistance may be related to the presence of insulin resistance and hyperinsulinaemia, they suggest.
Dr. Martell and colleagues studied 50 consecutive patients referred with refractory hypertension after excluding those with hypokalaemia and stenosis of the renal artery.
Ambulatory blood pressure was monitored in all patients, and antihypertensive drugs were withdrawn. Patients were also screened for secondary hypertension. In addition, these patients and a control group of essential hypertensives controlled with three antihypertensive drugs, underwent an oral glucose tolerance test.
Seven patients had primary normokalaemic hyperaldosteronism, two had pheochromocytomas, and six had white coat hypertension. The remaining 35 patients, confirmed as having truly resistant hypertension, showed significant differences in serum insulin levels and the homeostasis model assessment as an index of insulin resistance (HOMA IR) when compared with the control group.
"These findings show that among normokalaemic treatment-resistant hypertension, the presence of hyperaldosteronism and pheochromocytoma is quite high. Moreover, treatment resistance in hypertensive patients appears to be associated with insulin resistance," the researchers conclude.
"To our knowledge, this is the first study that includes the measurement of insulin resistance in refractory hypertension," they add.
They suggest that hyperinsulinaemia may increase blood pressure by several mechanisms, including stimulating the sympathetic nervous system, increasing renal sodium re-absorption, activating the Na+/H+ countertransport, and enhancing vessel wall cell proliferation and reactivity.
Blood Press 2003;12:3:149-154.
"High prevalence of secondary hypertension and insulin resistance in patients with refractory hypertension"
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