The authors, an obstetrician and a pediatrician, have collaborated for over a decade in the management of patients with ambiguous sexual development and other problems of sexual identity. This little monograph is a compilation of their experiences in this area. The theme of the monograph is a strong plea for accurate, early diagnosis and treatment of disorders of sexual development. The authors forcefully stress the importance of reinforcement of the selected sex of rearing in the minds of the patient and his family. Although these points are valid and important, they are by now widely accepted truths among physicians interested in the problems of sexual differentiation. The book has the unfortunate temporal position of following by one to two years other publications on the same topic which are more concise, more authoritative, and better referenced. The specific role of the genes, the testes, and the intrauterine hormonal factors which determine
We have attempted to determine the relative importance of dietary intake of protein and energy in restoring plasma immunoreactive somatomedin‐C (Sm‐C) concentrations after fasting. Ten healthy human volunteers were fasted for 5 days, then divided into two refeeding groups. One group (variable energy) was refed 1.0 g protein/kg ideal body weight, and in 9‐day sequences, 11, 18 and 25 kcal of energy/kg. The other group (variable protein) was given 35 kcal energy/kg, and in 9‐day sequences, 0.2, 0.4, and 1.0 g protein/kg. When subjects were refed the variable energy diets there was no significant increase in Sm‐C at 11 kcal/kg (0.47 ± 0.13 to 0.45 ± 0.12 U/ ml), suggesting that there is a threshold energy requirement below which optimal protein intake is not sufficient to raise the Sm‐C. When subjects were refed 18 and 25 kcal/kg, it became apparent that the more energy added to the diet, the greater the absolute concentration of Sm‐C attained (0.66 U/ ml on 18 kcal/kg and 0.97 U/ml on 25 kcal/kg). Sm‐C correlated with nitrogen balance (r = 0.58) during refeeding with the variable energy diets and was a good indicator of acute directional change in nitrogen balance. However, Sm‐C was not a reliable indicator of nitrogen repletion, since it rose almost to control levels on the 25 kcal/kg diet while nitrogen balance remained slightly negative. During refeeding of the variable protein‐adequate energy diets, there was a significant increase in Sm‐C at the lowest protein intake (at 0.2 g protein/kg, Sm‐C increased from 0.49 ± 0.22 to 0.80 ± 0.34 U/ml; p < 0.01), suggesting that the ingested energy facilitates the efficient utilization of small quantities of dietary protein. As more protein was ingested, the Sm‐C exceeded basal, prefast values in some subjects. Nitrogen balance correlated well with plasma Sm‐C (r = 0.71) on the variable protein diets and appeared to be a good indicator of acute changes in nitrogen accretion. These studies suggest that both energy and protein are important for restoration of Sm‐C after fasting. At extremely low levels of intake, however, it appears that energy restriction causes more impairment of the postfast recovery in plasma Sm‐C than does an equivalent restriction in protein intake. ( Journal of Parenteral and Enteral Nutrition 8 :407–411, 1984)
The ontogeny of somatomedin receptors in tissues of fetal pigs and levels of somatomedin- C in fetal pig serum at various gestational ages and in human cord serum was investigated. Specific binding of 125I somatomedin-C by particulate membranes prepared from fetal organs from a variety of gestational ages almost always exceeds specific I25I insulin binding. In liver, kidney, heart, and the maternal portion of the placenta, apparent binding affinity for somatomedin is relatively constant throughout gestation and is the same for membranes from fetal and adult animals. In contrast, in the fetal portion of the placenta, specific somatomedin-C binding and apparent binding affinity increases as gestation progresses. The changes in this tissue correlate temporally with the acceleration of growth of the pig fetus. Membranes prepared from fetal lungs exhibit higher specific binding of somatomedin and higher affinity constants than adult lung membranes. Somatomedin levels in fetal pig serum are about 25% of those observed in the sow and are constant throughout fetal life. Somatomedin in human cord serum is likewise low compared to adult levels. Small-for-gestational age infants and large, postmature infants have lower mean somatomedin levels than normal weight, full-term infants. The identification of specific somatomedin receptors in fetal tissues opens the possibility that somatomedin-C stimulates growth of the fetus. Although not resolved, the relatively low levels of somatomedin in fetal serum may reflect low levels of the somatomedin binding protein rather than an absolute deficiency of biologically active somatomedin.
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