Effect of octreotide on 24-h blood pressure profile in acromegaly

The aim of the study was to investigate the effect of octreotide, a somatostatin analog drug potentially able to inhibit growth hormone (GH), on the circadian blood pressure profile in a group of patients with acromegaly. Ten patients with GH-secreting pituitary adenoma were studied before and 6 months after treatment with subcutaneous octreotide 0.2 to 0.6 mg/day. Twenty-four hour blood pressure and heart rate were measured every 15 min at daytime (07:00 to 22:59) and every 30 min at nighttime (23:00 to 06:59) using a TM-2420 recorder. No correlation was found between GH levels and 24-h blood pressure in baseline conditions. Untreated patients had a significant nocturnal decrease of both systolic and diastolic blood pressure (P < .01), and all showed a circadian systolic or diastolic blood pressure rhythm. During octreotide treatment, 24 h as well as nighttime systolic and diastolic blood pressures significantly increased (P < .05), whereas daytime systolic and diastolic blood pressures did not change. Treated patients did not have a nocturnal decline in both systolic and diastolic blood pressures (P = NS), and eight lost their systolic or diastolic blood pressure rhythm. In conclusion, blood pressure circadian rhythm seems to be maintained in acromegaly. Octreotide treatment is associated with an increase of 24-h and nighttime blood pressure, and with loss of circadian blood pressure rhythm. Splanchnic vasoconstriction by this drug, shifting blood to peripheral vessels, may explain this phenomenon.