Thyrotropin-releasing hormone metabolism is attenuated in the cerebrospinal fluid of the human neonate.

The present study was designed to investigate the ontogeny of thyrotropin-releasing hormone (TRH) metabolism in human cerebrospinal fluid (CFS). The activity of pyroglutamate aminopeptidase (EC 3.4.11.8), the major enzyme catalyzing TRH metabolism in human CSF, was measured in CSF of 11 premature infants (gestational age, 29-39 weeks; birth weight, 1774 +/- 274 g), 8 newborn infants (term delivery; birth weight, 3648 +/- 240 g), and 11 adults (mean age, 29.6 +/- 1.5 years). Pyroglutamate aminopeptidase activity in CSF of premature and newborn infants was significantly lower (p less than 0.05) than that of adult CSF. These observed differences in the enzymatic activities were not due to changes in the affinity of the enzyme for its substrate TRH or the presence of enzyme inhibitor(s)/stimulator(s).