The effect of growth hormone (GH) replacement therapy on sympathetic nerve hyperactivity in hypopituitary adults: a double-blind, placebo-controlled, crossover, short-term trial followed by long-term open GH replacement in hypopituitary adults.
OBJECTIVE
To test whether sympathetic nerve hyperactivity associated with adult hypopituitarism and untreated growth hormone (GH) deficiency is affected by GH treatment.


METHODS
Sympathetic nerve activity to the muscle vascular bed (MSA) expressed as burst frequency (bursts/min) and incidence (bursts/100 heartbeats) was recorded in 10 hypopituitary patients (aged 48-69 years), before and after acute (1 week) randomized, double-blind, crossover treatment with a 1-month washout period and chronic (1 year) GH replacement treatment.


RESULTS
MSA burst frequency and incidence remained unchanged from baseline values after the short-term treatment, but exhibited decreases in median values [from 53 to 47 bursts/min (P = 0.02) and from 85 to 70 bursts/100 heartbeats (P = 0.03), respectively] after 12 months of replacement therapy. Twenty-four-hour urinary excretion of nitrate increased after the short-term cross-over treatment and the long-term treatment (P = 0.04). Diastolic blood pressure and waist circumference decreased after the 12-month treatment (P = 0.02 and P = 0.04, respectively). No correlation was found between the reduction in MSA and the increase in 24-h urinary nitrate excretion, the decrease in diastolic blood pressure and waist circumference.


CONCLUSIONS
The sympathoexcitation in adult GH deficiency and the modest decline in MSA seen after long-term GH replacement treatment may suggest that the somatotropic axis is involved in the regulation of central sympathetic outflow.
D000368:Aged; D001794:Blood Pressure; D001834:Body Water / Q000378:metabolism; D002302:Cardiac Output; D018592:Cross-Over Studies; D005260:Female; D005951:Glucose Tolerance Test; D020249:Hormone Replacement Therapy; D019382:Human Growth Hormone / Q000008:administration & dosage*; D006801:Humans; D007018:Hypopituitarism / Q000188:drug therapy* / Q000503:physiopathology; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D008055:Lipids / Q000097:blood; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000294:innervation; D009569:Nitric Oxide / Q000378:metabolism; D013564:Sympathetic Nervous System / Q000187:drug effects* / Q000503:physiopathology; D013963:Thyroid Hormones / Q000097:blood; D014655:Vascular Resistance; D016277:Ventricular Function, Left
D008055:Lipids; D013963:Thyroid Hormones; D019382:Human Growth Hormone; D009569:Nitric Oxide; D007334:Insulin-Like Growth Factor I