Role of the Thyrotropin-Releasing Hormone Stimulation Test in Diagnosis of Congenital Central Hypothyroidism in Infants

Abstract

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