Diurnal Variations of Plasma Luteinizing Hormone, Follicle-Stimulating Hormone, and Prolactin in Boys and Girls from Birth to Puberty

Thirty-eight girls and 44 boys were evaluated for nocturnal variations in plasma LH, FSH, and PRL. The children were subdivided into 4 groups according to their stage of sexual maturation. Blood samples were collected at 1800, 2200, 0200, and 0800 h from an indwelling venous catheter. The last sampling was followed by a simultaneous LHRH/TRH test to assess pituitary hormone reserve at different ages. In neither sex were differences of plasma LH values observed in age groups 1 and 2. In age group 3 (stages 2-3), girls demonstrated increased LH levels during sleep. The response to LHRH in this group was similarily high in girls and in girls and boys in age group 4 (stages 4-5). In the oldest group, a rise of plasma LH values at night occurred in both sexes. In girls, a significant nocturnal increase of plasma FSH values was found in age group 2 (prepubertal). In age group 3 (stages 2-3), boys also developed a nocturnal rhythm, with highest plasma FSH levels during sleep. Together with these increased nocturnal plasma hormone levels, a more pronounced response to LHRH stimulation occurred. Increased plasma PRL levels were found in all children at night without increasing basal values with the onset of puberty.