Deletion of a portion of the long arm of chromosome 18 is associated with growth hormone (GH) deficiency and hypogonadism. In order to further characterize the neuroendocrine axis in children with 18q- syndrome, a TRH stimulation test was performed on 5 affected children (age range 1-6 years, 3 female, 2 male). None were on hormonal replacement at the time of evaluation.

TRH (7 ug/kg) was administered i.v. and blood obtained at 0,15,30,45,60,90 and 120 minutes through an in-dwelling catheter (placed >30 minutes prior to Time 0). Four criteria were used to evaluate the response: 1)basal PRL (normal <18ng/ml), 2) peak/basal ratio(normal 3-5), 3) peak time (normal 15-30 minutes) and 4) post-peakdecline (60 min/0 min value, normal <2× basal). Table

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Basal PRL was normal in 3 children and elevated in 2, the peak/basal ratio was elevated in 2, the peak time was delayed in 2 and the post-peak decline was abnormal in 2. Only one child had a normal response as judged by all 4 parameters. This boy (2 year old) was GH deficient (GH peaks: 4.2,5.6 ng/ml) with an abnormal TRH response consistent with central hypothyroidism. Four additional GH deficient 18q- children on GH treatment for > 1 year were also tested (data not shown). One child was normal by all parameters, none had elevated basal PRL, 2 had low peak/basal ratios, 1 had delayed peak time and 1 had delayed decline. These results suggest that alterations in PRL production are common in children with 18q- syndrome (2/10 normal), as are the production of other hypothalamic/pituitary hormones. The clinical implications and causal mechanism(s) remain to be elucidated.