Serum growth hormone in patients with carcinoid tumours; basal levels and response to glucose and thyrotrophin releasing hormone

The regulation of serum growth hormone was studied in 33 consecutive patients with carcinoid tumours; both diurnal serum GH and GH responses to an i.v. glucose load and TRH were assessed. Seventeen of the patients (52%) showed disturbed regulation of serum GH and 10 had at least two abnormal tests. Four patients had clinically overt acromegaly. The diurnal mean serum GH levels were higher (P less than 0.001) in patients with carcinoid tumours than in control subjects and more than one third (41%) had levels in a range similar to that of acromegalic patients without carcinoid tumours. The disturbance in serum GH regulation might have been caused in some patient by tumour secreted growth hormone releasing factor(s) which act directly on pituitary somatotrophs, but other tumour-related non-specific stimulation must be considered. Carcinoid tumours should be considered in the aetiology of acromegaly.