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EXTRACTThe present studies in the newborn sheep were undertaken to further clarify the mechanism or mechanisms responsible for the early increases in serum thyroid hormone concentrations in the newborn as well as the significance of these changes to newborn nonshivering thermogenesis. Six groups of animals were studied to determine the influence of neonatal cooling, cord cutting, and the effects of thyrotropin-releasing hormone ( T R H ) and triiodothyronine iT3) iniections. ~ , . ,Group I newborns were delivered into room air with immediate cord cutting. Group I1 animals were delivered into room air and cord cutting was delayed 60 min. Group III animals were delivered into a 39' water bath and maintained for 60 min with the umbilical cord intact; the cord was cut at the time of removal from the water bath. Group I V animals were handled similarly to group 111 animals except that cord cutting was delayed 60 min after removal from the water bath. Group V and VI newborns were handled similarly to group I V animals except that T R H (group V) or T 3 (group IV) was injected at the time of removal from the water bath. Deep rectal temperature and serum free fatty acids (FFA), thyroxine (T4), and T 3 concentrations were measured in all newborns; FFA was measured as an index of catecholamine release. Serum thyroid-stimulating hormone ( T S H ) was measured in newborns from groups I and II.The results indicate that the newborn lamb responds to par turition similarly to the human newborn. There are marked increases in mean serum T 3 (50-242 ng/100 ml) and FFA levels (245-744 pEq/liter) during the first 60 min with only a transient fall in body temperature (39.1' to 37.4"), indicating effective nonshivering thermogenesis. Serum T 4 concentrations do not increase significantly during this time. Warming in the water bath (groups III and IV) prevented the FFA and T 3 responses, indicating that parturition per se is not the stimulus to these events. Delayed cord cutting (groups II and IV) produced marked hypothermia (to 35.6 and 34.4"), and the increases in serum FFA and T 3 concentrations were not observed until the cord was cut.Mean baseline serum T S H concentrations were 4.7 and 5.3 pU/ml, respectively, in groups I and II animals and increased modestly to peak values a t 30-60 min whether or not the umbilical cord was cut. T R H (group VI) did not increase serum T 3 levels during the first 60 min, but a significant 4-hr response (to 336 ng/100 ml) was observed. T 3 (group VI) did not stimulate the FFA or thermogenic responses directly, but significantly augmented both responses to cord cutting. In addition, there was a significant correlation between serum FFA or T 3 concentrations 60 min after cord cutting and minimal rectal temperature ( r = 0.53 and 0.71, respectively; P < 0.005).The present results indicate that in the newborn sheep: ( I ) umbilical cord cutting, rather than cooling, stimulates FFA release, T 3 production, and nonshivering thermogenesis; (2) that the early T 3 response is not mediated via T R H and TSH...

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Daily production (PR) of human growth hormone (I-IGH) was calculated in patients with juvenile diabetes and control subjects by determining metabolic clearance rate (MCR) of isiI HGtI, at equilibrium, and mean endogenous HGH levels throughout a 24 h day. Half hourly sampling or a constant withdrawal pump were used to obtain an integrated mean endogenous tIGtt level MCR (liters/day) was significantly reduced in all diabetic subjects both in absolute terms (96 4-15 vs 274 4-37) and relative to surface area (624-8 vs 171 4-21) (p < 0.01). Mean HGH levels were 8.4 ng/ml in the diabetics and 5.5 ng/ml in age matched controls. Daily ttGH PR in the diabetic subjects (339 to 1365 ~g/day) did not exceed values in the control subjects (1005-1426 ~g/day). The results indicate that the elevated plasma I-IGH levels and increased I-IGtt response to stimuli observed in diabetes, reflect reduced metabolic clearance, rather than increased pituitary secretion.

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