Endocrine Abstracts

Objective: To evaluate the reliability of GH stimulation tests in multiple pituitary hormone deficiency (MPHD) and isolated GHD.

Materials and methods: In 19 children with MPHD, we analysed the results of insulin tolerance test (ITT), clonidine and sleep tests, anthropometric parameters, IGF1, bone age, pituitary hormone levels±MRI. GH provocation tests were repeated after variable periods, mostly 6–24 months. The GH provocation tests were considered positive, if peak GH-value <10 ng/ml. The results were compared with those obtained in 15 children with isolated GHD (with harmonic short stature, height-SDS<3 S.D., reduced IGF1 and bone age, at least one GH stimulation test positive).

Results: In children with MPHD, the mean age at diagnosis was 11.25±3.48 years and mean height-SDS −5.00±(−1.40) S.D. Thyroid and adrenal function were normalised before GH provocation tests. ITT and sleep tests were positive in all children, clonidine test was false-negative in 3 cases (15%). IGF1 before rhGH-therapy was decreased in 81.2% cases. Bone age before rhGH therapy was delayed with 1.4–9.25 years (mean: 4.61±2.2 years). In children with isolated GHD mean age at diagnosis was 9.69±3.65 years, mean height-SDS −4.00±(−0.61) S.D., bone age delayed with 3.41±1.58 years. False-negative results were obtained in 4.7% of ITT, 15.7% of clonidine tests and 20% of sleep tests, thus GH stimulation tests were discordant in five children (1/3 of isolated GHD).

Conclusion: The results of GH stimulation tests were discordant in 15.8% of MPHD (due to false-negative clonidine test), but more frequently (in 1/3 of children) in isolated GHD, even if IGF1 and bone age sustained the presumed diagnosis. We consider that in isolated GHD at least two tests should be used, mainly if the first GH provocation test is below the cut-off level.