Postnatal Surge in Serum Calcitonin Concentrations: No Contribution to Neonatal Hypocalcemia in Infants of Diabetic Mothers

Abstract

MAT ERIALS AND METH OD S (2, 3). However, it was shown in a prospective, matched-control study that NHC in IDM is significant even after contro lling for the aforementioned variables ( I). Leadin g theori es related to th e path oph ysiology of NHC in IDM includ e: 1) maternal-fetal Mgdeficient state, du e to matern al glycosuria (4), leading to fetal hypoparath yroidism and subsequent NH C ( I, 5) and 2) neonatal hyperca lcitoninemia (6, 7). The latter theory is supported by evidence that the neonatal surge in serum CT concentrations found in normal neonates also occurs in IDM , which might seem inappropriate when one considers the concomitant decrease in serum Ca. Stu dies supporting th is theory were limited by sma ll sample size, with only one showing an inverse correlation between serum Ca and CT conce ntrations in II IDM (6). We conducted this prospective study to determine whether CT plays any role in NHC in IDM when simultan eous measurements of serum Mg and PTH concentrations are taken int o account.Patients. Since 1979,47 full-term (37-4 1 wk gestation) infants of insulin-dependent diabetic mothers (White classes B-RT) (8) were prospectively studied as part of an NIH-funded program project grant, "Diabetes in Pregnancy." Preterm infants were excluded from this study because of the confounding influences of gestational age on neonatal calcium metabolism (I). The 47 IDM were compared with a group of 31 term infants of nondiabetic pregnant women [norm al glucose challenge test at 28 wk gestation (9)] born after un com plicated pregnan cies, labors, and deliveries. Th is study was approved by the Review Board on Investigations Involving Human Beings of the Uni versity of Cincinn ati Medical Center Hospital. Written informed consent was obtained from one of the legal guardians of each infant before enrollment int o the study.Th e aims of glycemic cont rol in diabetic pregnan cy were a preprandial blood glucose concentration below 5.55 mm ol/L ( 100 mg/dl. ) and a 90-min postprandial blood glucose concentration below 7.7 1 mrnol/ L ( 140 mg/dl.). Pregnant patients were hospitalized when necessary to maint ain these goals of glycem ic contro l. Matern al blood glycosylated Hb A I contents were measured every 4 wk to determine if adequ ate glycemic control was achieved. Pre-or postprandial capillary glucose concentration was alterna tively measured at each weekly visit. In each patient, pre-or postprandi al blood glucose values were averaged over each trimester as mean pre-or postprand ial blood glucose concentrations per trim ester (10).Data collection. Diabetes was categorized using the Whit e classification (8). Blood samples were collected from infants in both groups at birth from a double-clamped segment of umbilical cord and at 24 h of life for determination of Ca, Mg, PTH, and CT. Gestational age was calculated from the last menstrual period and confirmed within ± 2 wk of Ballard score (10). We defined NHC, using the traditional definition supported by the data 493 Abbreviations IDM, infant of diabetic ...

Bone Development and Mineral Homeostasis in the Fetus and Neonate: Roles of the Calciotropic and Phosphotropic Hormones

“…Subsequent studies used intact PTH assays but obtained measurements solely at birth and 24 h later, and demonstrated that PTH rose significantly (31,386,388,416,444,473,580). Those studies did not determine when the PTH value increased or whether the peak level was achieved at 24 h or later.…”

“…Calcitonin may increase up to 10-fold over cord blood levels during the first 48 h after birth (32,53,444,595), before gradually declining over the subsequent days or weeks (32,583).…”

“…A few early studies suggested that the normal high calcitonin levels in the neonate could contribute to hypocalcemia in preterm infants (558,583,595). However, subsequent studies found that gestational age at birth was a more significant determinant of neonatal calcitonin levels than the postnatal fall in serum calcium or the development of hypocalcemia (444,558,707). Therefore, the available human data suggest that calcitonin may have little role in mineral homeostasis of the neonate.…”

Effect of Magnesium Sulfate Concentration on Serum Ionized Magnesium In Vitro

“…12 However, these compensatory mechanisms may not be very effective in young neonates, who are known to have impaired regulation of PTH secretion 13,14 as well as of calcitonin secretion. 15 Another limitation of our study is that the serum samples studied were basically ''normal'' samples, and we can only speculate that the relationship between serum Mg 2þ and serum Mg may be even more pronounced in hypoproteinemic samples, 16 as predicted by the law of mass action. Indeed, if there are fewer albumin binding sites available for Ca or Mg because of hypoproteinemia, the addition of a small amount of Ca or Mg will have a larger effect on the binding of the other ion.…”

Influência do crescimento intra-uterino restrito e da asfixia perinatal sobre os níveis séricos de magnésio em recém-nascidos de termo na primeira semana de vida

“…Em adultos saudáveis, não se observou diminuição do Mgi ou MgT circulante após injeção de glucagon (Mimouni et al,1990), enquanto no rato, o glucagon pode aumentar a reabsorção de Mg na alça de Henle e nos túbulos distais. As ações do glucagon e ADH foram aditivas e são mediadas pela adenil-ciclase e AMPc.…”