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Thyrotropin response to thyrotropin-releasing hormone in fullterm, euthyroid and hypothyroid newborns
Insights
Thyroid-stimulating hormone (TSH) levels in newborns were assessed. Euthyroid infants showed adult-like TSH responses to thyrotropin-releasing hormone (TRH), while hypothyroid infants had very high TSH levels.
Area of Science:
- Endocrinology
- Neonatal Medicine
- Pediatric Endocrinology
Background:
- Thyrotropin (TSH) regulation is crucial in newborns.
- Understanding the TSH response to thyrotropin-releasing hormone (TRH) is vital for diagnosing thyroid dysfunction in neonates.
Purpose of the Study:
- To investigate serum TSH concentrations and TRH stimulation response in euthyroid and hypothyroid newborns.
- To compare the TSH response in newborns to that observed in adults.
Main Methods:
- Serum TSH levels were measured in 16 euthyroid and 2 hypothyroid infants at various time points after birth.
- TSH was assessed before and at 30 and 180 minutes after intravenous TRH injection (40 mug).
Main Results:
- Euthyroid newborns exhibited transiently elevated basal TSH shortly after birth, followed by a decline.
- The relative TSH increase following TRH stimulation in euthyroid neonates was comparable to adults.
- Congenital hypothyroid infants presented with markedly elevated basal TSH levels (125 and 400 muU/ml) without a significant response to TRH.
Conclusions:
- The relative serum TSH response to TRH in euthyroid full-term newborns is similar to adults, despite higher thyroid hormone levels.
- In congenital hypothyroidism, extremely high basal TSH levels are observed, rendering supplementary TRH testing diagnostically redundant.
Abstract:
The serum concentration of thyrotropin (TSH) and the TSH response following thyrotropin-releasing hormone (TRH) were studied in 16 euthyroid babies from 16 to 172 hours after birth and in 2 primary hypothyroid babies, 3 and 28 days of age. Serum-TSH was measured before an intravenous injection of 40 mug TRH and after 30 and 180 min. In the euthyroid babies increased basal levels of TSH were seen shortly after birth, followed by a pronounced decline. The extent of TSH increase after TRH could be correlated with the basal levels, and the relative increase was comparable to that which occurs in adults. In the hypothyroid babies very high basal levels of serum-TSH were seen, 125 and 400 muU/ml respectively, with no further increase following TRH stimulation. It was concluded that in euthyroid fullterm newborn, the relative response of serum-TSH to TRH was equal to that of adults, in spite of elevated thyroid hormone concentrations. In the hypothyroid newborn very high levels of serum-TSH were seen and a supplementary TRH-test seems without diagnostic value in congenital hypothyroidism.