Outpatient assessment of residual growth hormone secretion in treated acromegaly with overnight urinary growth hormone excretion, random serum growthhormone and insulin like growth factor-1

OBJECTIVE To assess the outpatient investigations, overnight urinary growth hormone (uGH) excretion, random serum GH and insulin like growth factor 1 (IGF-1), and GH indices from the oral glucose tolerance test (OGTT) (fastin g, nadir and mean GH), as measures of mean GH secretion in treated acromega ly, in comparison with a GH day series, which served as a gold standard. DESIGN Prospective cross-sectional study, with patients admitted to a metab olic ward for the following investigations: random GH, IGF-1, 6 point GH da y series (day 1), 9 h timed overnight uGH excretion, OGTT with GH response (day 2). Agreements between the mean GH during the day series and the other outcome measures, and the diagnostic performance of the latter, for the pr esence or absence of active acromegaly (mean GH during day series greater t han or equal to 5 or < 5 mU/ I, respectively) were determined. PATIENTS 26 patients with treated acromegaly (11 with inactive acromegaly o ff drug therapy). MEASUREMENTS Serum GH and uGH were measured by immunoradiometric assays and IGF-1 by radio-immunoassay. RESULTS Agreements with the mean GH during the day series were perfect for the nadir GH during the OGTT with a 2 mU/l cutoff (Cohen's kappa (kappa)=1, P<0.00001), almost perfect for the fasting and mean GH throughout the OGTT (both kappa=0.92, P<0.0001) and random GH (kappa = 0.85, P< 0.0001), and s ubstantial for the nadir GH with a 5 mU/l cutoff (kappa=0.77, P<0.0001), IG F-1 (kappa=0.62, P<0.001) and overnight UGH excretion (kappa=0.61, P=0.002) . Nadir GH with a 2 mU/l cutoff was completely accurate for diagnosing the presence or absence of active acromegaly (positive and negative predictive values (%+/-: standard error percentage) 100 +/- 8% and 100 +/- 10%). None of the outpatient tests used atone was an adequate diagnostic test (positiv e and negative predictive values: overnight uGH excretion -86+/-10% and 75/-13%; random GH -100+/-11% and 85+/-11%; IGF-1 - 92+/-10% and 71+/-13%) an d so combinations of tests were assessed. The best was overnight uGH excret ion plus random GH (positive and negative predictive values 88+/-9% and 100 +/-12%). Using all three outpatient investigations, the positive predictive Value of three raised results was 100+/-13%. CONCLUSIONS In treated acromegaly, residual GH secretion can be reliably as sessed with the OGTT, using standard diagnostic criteria. It can also be as sessed on an outpatient basis with overnight uGH excretion and random GH, a s direct measures, and IGF-1. If these are all normal, active acromegaly is excluded. Three raised results denote active acromegaly, and one or two ra ised results would need further investigation with a GH day series.