SUMMARY The significance of calcium soap formation in the inhibition of calcium absorption has been studied in rats. 47Ca labelled soaps of fatty acids were introduced into the duodenum and the absorption of calcium measured after four hours in a whole body counter. The absorption of calcium was inversely correlated with the chain length of the fatty acid varying from 1 % for Ca-stearate to 60% for Ca-hexanoate. Increasing the degree of unsaturation of the fatty acid was accompanied by increased calcium absorption. The availability of calcium for absorption from the soaps was correlated with their solubility in 1 % aqueous Na-tauroglycocholate. The percentages of calcium as soap in the small intestine and the faeces after intragastric administration of calcium and fats were similar, which suggests that the faecal content of calcium soaps is an index of intestinal soap formation. Soap formation was negligible when CaCl2 was given with tristearate, trioleate, or tridecanoate and no depression of calcium absorption was observed. Calcium absorption was markedly impaired by the addition of phosphates at a Ca/P ratio of 1:1 irrespective of the presence of neutral fats. Stearic acid resulted in significant soap formation and reduced calcium absorption. The degree of Ca-soap formation and the inhibition of calcium absorption were well correlated. The results suggest that, although calcium soap formation may markedly depress calcium absorption in the rat, no significant soap formation takes place when fats are given in the form of triglycerides.

The daily excretion of C-peptide in the urine was measured in 105 healthy infants and children from birth to 14 years of age. For technical reasons no studies were performed from 1-3 years of age. The excretion of C-peptide showed a close positive correlation with age and weight. The relationship with weight was already apparent in the 1st days of life. The C-peptide/weight and the C-peptide/creatinine ratios were constant throughout most of childhood with the exception of the age range of 1 month-1 year when the C-peptide/creatinine was significantly higher. In obese children the C-peptide/weight and C-peptide/creatinine ratios were similar to those found in children with normal weight. In growth hormone deficiency these ratios were low and increased during the 1st week of growth hormone therapy. It is concluded that urinary C-peptide is a reliable indicator of integrated insulin production and gives new information about insulin secretion in various conditions.

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Growth hormone response was studied during long term corticosteroid treatment in 13 children. Arginine infusion was used as the stimulus of growth hormone release. The growth hormone levels were significantly higher in the steroid treated group than in normal controls. There was no correlation between the dose of the drug or the duration of the treatment and growth hormone concentration.

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