Heart rate increases in patients with growth hormone receptor deficiency treated with insulin‐like growth factor I

Cardiac function was measured in 16 prepubertal Ecuadorean patients with growth hormone receptor deficiency given insulin‐like growth factor I (IGF‐I) during part of a clinical trial. The IGF‐I was given subcutaneously twice daily at a dose of 40 μg/kg on days 1 and 2, 80 μg/kg on days 3 and 4, and 120 μg/kg thereafter. Heart rate was determined at baseline (pretreatment) and on days 1–7 by repeated palpation of the radial artery and at baseline and on days 2, 4 and 7 by continuous portable Holter monitoring. Heart rate measured by both methods rose progressively with increasing doses of IGF‐I. The mean palpated pulse exceeded baseline on each treatment day and was significantly higher on day 5 than day 4 and significantly higher on day 3 than day 2. The mean Holter heart rate was significantly higher on day 4 than on day 2 and significantly higher on day 2 than at baseline. Non‐significant glucose and electrolyte changes did not appear to be associated with the cardiac events.