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Evidence for transient peripheral resistance to parathyroid hormone in premature infants
Insights
Preterm infants show a transient pseudohypoparathyroid-like state in their first week, with immature renal response to parathyroid hormone (PTH). This condition may contribute to hypocalcemia in premature infants.
Area of Science:
- Neonatology
- Pediatric Endocrinology
- Mineral Metabolism
Background:
- Preterm infants often experience hypocalcemia.
- Parathyroid hormone (PTH) plays a crucial role in calcium homeostasis.
- Understanding PTH's action in preterm neonates is vital for managing metabolic complications.
Purpose of the Study:
- To investigate parathyroid hormone (PTH) levels and related biochemical markers in preterm infants during the first four weeks of life.
- To assess the maturation of renal and bone response to PTH in this population.
- To explore the potential link between PTH dynamics and hypocalcemia in prematurity.
Main Methods:
- Measured serum immunoreactive parathyroid hormone (iPTH), ionized calcium, and urinary cyclic AMP/creatinine ratio (cAMP/Cr).
- Assessed bone turnover markers: alkaline phosphatase (AP), serum osteocalcin, and urinary hydroxyproline/creatinine ratio (OH-P/Cr).
- Analyzed data from 26 preterm infants over the first four weeks of life, correlating various parameters.
Main Results:
- Initially, despite stimulated PTH, urinary cAMP/Cr and bone turnover markers were low, suggesting a pseudohypoparathyroid-like state.
- PTH levels decreased, while cAMP/Cr and bone turnover markers increased, normalizing by weeks 2-3.
- Correlations between iPTH and cAMP/Cr shifted from negative to positive, indicating maturing renal response to PTH.
Conclusions:
- Preterm infants exhibit a transient pseudohypoparathyroid-like state in the first week of life due to immature renal and possibly bone response to PTH.
- This immature response may be a significant etiological factor in the hypocalcemia observed in premature infants.
- The findings highlight the dynamic changes in mineral metabolism and PTH responsiveness during early postnatal development in preterm neonates.
Abstract:
Serum immunoreactive parathyroid hormone (iPTH), ionized calcium, the urinary cyclic AMP/creatinine ratio (cAMP/Cr) and some indices of bone turnover (alkaline phosphatase (AP), serum osteocalcin, and the urinary total hydroxyproline/creatinine ratio (OH-P/Cr)) were measured in 26 preterm infants during the first 4 weeks of life. Despite of stimulated parathyroid gland activity cAMP/Cr, AP, osteocalcin and OH-P/Cr were low during the first week. Thereafter iPTH decreased, whereas cAMP/Cr, and the indices of bone turnover increased, reaching high-normal values (in comparison to full-term infants) during the second and third week of life. Serum iPTH was negatively correlated to cAMP/Cr in the first week (r = -0.61, p less than 0.01), whereas the relationship became positive during the second (r = 0.47, p less than 0.05) and third (r = 0.54, p less than 0.05) week of life indicating maturation of the renal response to PTH. The study supports the concept that in premature infants a transient pseudohypoparathyroid-like state is present during the first week of life reflecting an immaturity of renal and possibly bone response to PTH. This may be an etiological factor in hypocalcemia of prematurity.