Pituitary-gonadal function in XYY and XXY men identified in a population survey

Evidence on pituitary-gonadal function in XYY subjects has been inconclusive and based, for the most part, on selected samples such as institutionalized individuals or subjects examined for particular behavioural or medical characteristics. We report the results of a double-blind hormonal study of a sample from an entire well-defined birth cohort of men. The starting population included all males born in Copenhagen during the period 1944-1947 comprising 31,436 individuals. Chromosome determinations conducted on 4139 men representing the top 15.9% of the height distribution of the sample identified 12 XYY and 16 XXY men. All the XYY subjects and 14 XXYs consented to participate in an individual case study and were individually matched to XY controls selected from the total sample. The XYY men had significantly higher plasma concentrations of LH, FSH and testosterone than matched XY controls. There were no differences in testicular size and in the reported number of children between the XYYs and control group. XXY men from the same population showed significantly higher LH and FSH, lower concentrations of testosterone, had smaller testes and reported fewer children than their matched controls.