Endocrine Abstracts

Background: To minimise the risk of false-positive Growth Hormone (GH) test results, UK guidelines recommend performing two GH stimulation tests to diagnose GH deficiency. In contrast, the possibility of false-negative results is rarely discussed. We present cases in two male children who had normal GH levels on stimulation testing, yet their auxological and clinical features were consistent with GH deficiency. Both were commenced on GH treatment with positive clinical and growth responses.

Results: Case 1 presented at 4.1 years of age with a height of -3.2 SDS. The baseline IGF-I was 6.4 nmol/l (2.9 - 27). Pituitary function tests were normal with a peak GH of 7.6 mg/l. A metabolic and growth failure in early childhood gene panel were negative. Given persistent clinical suspicion of GH deficiency he had a trial of GH. The HV improved to 9.6 cm a year (height -1.27 SDS). After 4.8 years of treatment his height is -0.34 SDS. The MRI scan of his head was normal. Case 2 presented at 2.1 years of age with a height of -3.9 SDS. Pituitary function testing was normal with a peak GH of 8.2 mg/l. The IGF-1 remained undetectable before and after an IGF-1 generation test, thus primary IGF-1 deficiency was suspected. The options of a trial of GH or recombinant IGF-1 were discussed. GH was considered more practical initial therapy and the HV improved to 16.7 cm/year and height increased by 1.6 SDS in a year. An MRI showed an abnormal pituitary and absent pituitary stalk.

Conclusion: These two cases highlight the importance of prioritising clinical judgement when evaluating children with short stature. Despite normal GH levels on testing, both boys demonstrated significant catch-up growth following treatment. These cases highlight the potential for false-negative results in GH testing. An MRI of the pituitary region should be considered as part of the diagnostic workup if clinical suspicion remains. The boys’ positive growth responses provide biological confirmation of GH responsiveness, supporting the use of a therapeutic trial of GH in selected cases.