Background: The investigation of short stature includes evaluation of a number of clinical, radiological, and biochemical factors. This often includes dynamic function testing to rule out abnormalities of the hypothalamicpituitary axis to rule out GH deficiency (GHD). NICE guidance advises that two GH stimulation tests demonstrating subnormal GH peak <6.7 μg/ml (20 mU/l) is required to confirm the diagnosis of GHD.
Objectives: To interrogate various clinical and biochemical parameters to reduce the need for dynamic function testing in the diagnosis of isolated GHD (IGHD) vs idiopathic short stature (ISS).
Methods: A retrospective case-review of all patients in a single centre from 2002 to 2014 undergoing two provocation tests.
Results: 138 patients underwent GH testing, 32% (45) had a normal GH peak (>6.7 μg/l) on repeat testing.
|Gender||27F: 66M (n=93)||13F: 32M (n=45)|
|Age at first assessment||8.1 (0.9516.29; S.D. 4.2)||7.9 (1.0914.1; S.D. 3.7)||NS|
|BA delay||−1.1 (−5.2 to 2.8; S.D. 1.33)||−0.86 (−5.8 to 1.5; S.D. 1.2)||NS|
|Low IGF1||37 (39.8%)||10 (22%)||NS|
|HV SDS pre-test||−0.86 (−5.9 to 5.1; S.D. 2.1)||−0.5 (−5.3 to 11.85; S.D. 3.3)||NS|
|HV SDS 1 year post test||2.36 (−4.3 to 13.6; S.D. 3.5)||0.6 (−5.2 to 7.2; S.D. 3.5)||0.016|
|Final height SDS||−0.92 (−5.6 to 1.8; S.D. 1.9)||−1.19 (−2.2 to 0.6; S.D. 0.9)||NS|
Conclusions: Approximately one-third of patients who undergo dynamic function testing for GHD will have a normal GH peak on re-test. We have previously shown that there is no cut-off on the first test that will predict an abnormal second test. There is no difference between IGHD vs ISS in terms of mean BA delay, IGF1 levels and pre-test HV SDS which improves the pre-test probability of having a low GH peak on two tests. There is a significant difference between HV SDS between IGHD and ISS 1 year after dynamic testing, reflecting the effect of GH treatment in IGHD. There appears to be no significant difference in final height outcomes in either group. At present, undertaking two GH stimulation tests appears to be the best way to distinguish IGHD from ISS.