The TRH test is used in the diagnosis of hypothalamic-pituitary (hp) disorders in children. It is unclear how often the result of this test is helpful. We have examined the results of TRH testing in 143 children investigated primarily for disordered growth. Children with hp axis tumours were excluded.
The TSH response to TRH (5microg/kg iv) was defined as abnormal if the peak TSH was <5mU/L (pituitary), or if the peak TSH at 60 mins was higher than at 20 mins (hypothalamic), or if the basal TSH was >5mU/L and/or the peak was >35mU/L (hyper-responsive). Basal fT4 was normal in 126 of the TRH tests and low in 17. In those with a normal fT4, 31 (25%) TRH tests were abnormal. In those with a low fT4, 11 (65%) were abnormal.
116 children had had a TRH test (with normal fT4), a GH stimulation test and an hp axis MR scan (abnormal if anterior lobe hypoplastic, stalk absent, or ectopic posterior pituitary (EPP) present). In 31 children with normal MR and GH status (peak GH >15mU/L), 20 (65%) had a normal TRH test, confirming normality. For the remaining 11 with abnormal TRH tests, follow-up of thyroid function was indicated. In the 43 with an abnormal MR and GH status, 11 (26%) had an abnormal TRH test, providing confirmation of an hp disorder and indicating the need to re-evaluate thyroid status. In the remaining 42 children with discordant MR and GH results (one or the other abnormal), 5 (12%) had abnormal TRH tests.
This audit has indicated that 26% of those with an abnormal hp axis MR and low GH had a normal fT4 but abnormal TRH test. The TRH test, as one part of the investigation for hypopituitarism, does aid diagnosis and guide management in a significant number of children.
22 - 24 Mar 2004
British Endocrine Societies