TEMPORARY LOSS OF A METABOLIC RESPONSE TO COLD STRESS IN INFANTS OF LOW BIRTHWEIGHT

Studies of thermo-regulatory ability have been undertaken at regular intervals throughout the first 6 weeks of life in a series of 28 infants who weighed between 1 and 2 kg. at birth. Three infants were encountered who had normal responses at birth, but lost much of their ability to increase heat production in a cool environment while in hospital at between 5 and 10 days of age, so that body temperature fell rapidly whenever they were exposed to a cool environment. The infants appeared well at the time this reduced response was first detected. The other factors involved in the normal physiological control of body temperature did not appear to be disturbed. Low birthweight, together with low incubator temperature in the first few days of life at a time when calorie intake was low, might be implicated in the observed temporary loss of metabolic response to a cold stress of 29 °C. for 20 minutes. 2 of the 3 infants were of low birthweight for their length of gestation; gastro-enteritis may have been an aggravating factor in the third infant. The defect in temperature regulation was only temporary, and could have resulted from depletion of the fat stores available to the babies' calorigenic brown adipose tissues.