Role of the thyrotropin-releasing hormone stimulation test in diagnosis of congenital central hypothyroidism in infants.

CONTEXT: A shortage of thyroid hormone during prenatal life and the first years after birth results in a spectrum of neuropsychological disorders, depending on the duration and severity of the deficiency. In the case of congenital hypothyroidism of central origin (CH-C), the majority of patients have multiple pituitary hormone deficiencies (MPHD). This condition poses an additional threat to postnatal central nervous system development, primarily on account of neuroglycopenia due to ACTH/cortisol deficiency with or without additional GH deficiency. Therefore, in CH-C, rapid diagnosis is even more urgent than in congenital hypothyroidism of thyroidal origin.

OBJECTIVE

In the assessment of hypothalamic-pituitary-thyroid function, we considered the pituitary response to iv administration of TRH (TRH test) pivotal. We evaluated the usefulness of the TRH test in a cohort of infants with neonatal congenital hypothyroidism screening results indicative of CH-C by analyzing the results within the framework of investigations of the anatomical and functional integrity of the hypothalamo-hypophyseal system.

DESIGN AND

SETTING

The study was a Dutch nationwide prospective study (1994-1996). Patients were included if neonatal congenital hypothyroidism screening results were indicative of CH-C and patients could be tested within 3 months of birth.

PATIENTS: Ten male and five female infants with CH-C, detected by neonatal screening, and six infants with false-positive screening results, nonthyroidal illness, or transient hypothyroidism, were included in the study.

MAIN OUTCOME MEASURES: Results of TRH tests, within the framework of extensive endocrinological examinations and cerebral magnetic resonance imaging, were measured.

RESULTS

All patients with type 3 TSH responses to TRH had MPHD, and the majority (67%) of patients with type 2 responses had isolated TSH deficiency.

CONCLUSIONS

The TRH test has a pivotal role in the diagnosis of TSH deficiency in young infants. Abnormal TRH test results, especially a type 3 response, urge immediate assessment of integral hypothalamic-pituitary function because the majority of patients have MPHD.