Endocrine Abstracts

PTHrP is an important factor for the regulation of calcium homeostasis around delivery. The aim of this study was to longitudinally analyse PTHrP metabolism and influencing factors looking at mothers and their breastfed newborns from 32 weeks of pregnancy until 8 weeks after delivery. Nineteen families (8 Caucasian, 11 Arabic/Asian) participated in the study. We analysed PTHrP, 25 OH vitamin D, parathyroid hormone (PTH), alkaline phosphatase, albumin; serum and urine calcium, phosphate and creatinine. Measures were obtained at 32 weeks of pregnancy (mothers), from cord blood and at 5 days and 8 weeks after delivery (mothers and infants). UVB exposure was continuously quantified by spectral analysis using bio-weighted dosimeters. Surrounding factors and nutrition were assessed by questionnaires and analysis of meteorological data.

Around delivery PTHrP-levels of mothers peaked to a level that was maintained subsequently (pmol/l±S.E.M., 32 week/cordblood/day5/8weeks): 0.26±0.1/0.56±0.1/0.58±0.1/ 0.54±0.1, P<0.05. In newborns PTHrP on day 5 decreased compared to cord blood levels and remained low (pmol/l±S.E.M., cordblood/day5/8weeks): 0.54±0.1/0.27±0.1/0.35±0.1, P<0.005. Regression analysis revealed that PTHrP levels between mothers and their children were not correlated. Subjects with mildly pigmented skin (WHO types I and II) had higher PTHrP-levels (P<0.005). PTHrP was positively correlated with sun exposure demonstrating seasonal variations (P<0.05). PTHrP was inversely correlated with 25 OH vitamin D (P<0.05) and not dependent on PTH and calcium levels.

These results reflect that PTHrP is of importance for mothers around delivery and during lactation and for newborns around delivery. It is the first study to demonstrate a longitudinal effect of sun exposure, seasonality, skin type and vitamin D on PTHrP metabolism.