URINARY CATECHOLAMINE EXCRETION IN INFANTS OF DIABETIC MOTHERS

Abstract

A transient, often profound, hypoglycemia is usually found in newborn infants of diabetic mothers. Normally, hypoglycemia results in large increases in urinary catecholamines, mainly as the adrenaline fraction. Multiple excretion rate studies were carried out in 21 infants of diabetic mothers in hypo ("low") and normoglycemic ("high") periods assigned on the basis of blood sugars below or above 40 mg/100 ml. Mean level was 25 mg/100 ml (range, 7 to 39) for the "low" and 72 mg/100 ml (range, 45 to 133) for the "high" periods. Mean urinary catecholamines were for adrenaline, 0.030 ± 0.006 nanograms(ng)/kg/minute in the "high" and 0.029 ± 0.009 ng/kg/minute in the "low" periods. For noradrenaline the comparable values were 0.388 ± 0.060 ng/kg/minute falling to 0.281 ± 0.044 ng/kg/minute. In 16 of the 21 infants comparative studies were available for each infant in both periods. Analyzed as the differences between pairs, there was no change in adrenaline but a highly significant (p < 0.001) decline in noradrenaline following hypoglycemia. In addition to the failure of the anticipated hypoglycemic increase, the resting (normoglycemic) levels for both fractions were extremely low compared to two groups of normal infants within the first 24 hours, as well as the first week, of life. These findings are suggestive of an adrenal medullary exhaustion phenomenon consistent with the view that the hypoglycemia is of long standing (intra-uterine) duration. The seemingly inappropriate noradrenaline depletion is likely a reflection of the different composition of the neonatal as opposed to the adult gland.