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Male weanling rats were fed four diets providing high or low levels of protein and/or zinc. One group on each diet was sacrificed every 2 weeks to measure the weights of the reproductive organs, plasma levels of follicle-stimulating hormone and luteinizing hormone, and the plasma and testicular concentrations of testosterone, dihydrotestosterone and zinc. The results demonstrate that hypogonadal states are produced in response to protein deficiency and zinc deficiency but the mechanisms involved are different. The specific effects of zinc deficiency are not observed in protein-deficient animals.

The mean ages of attainment of successive stages of puberty were estimated in a cross-sectional sample of 453 Egyptian schoolboys from a semi-urban area of Cairo, ranging in age from 9 to 17 years. The stages of puberty were as defined by Tanner (1962). The mean age of onset of puberty (stage 2) was 11.1 years, assessed either by genitalia or by pubic hair. Stage 5 occurred at 16.2 years, again both for genitalia and pubic hair. The time interval between these ages, 5.1 years, was 2 years longer than for British or Chinese boys. There was a highly significant effect of social class on the mean ages of attainment, and the heights and weights of the boys were also related to social class, the class 1 boys being taller and heavier than Tanner's British boys.