Collagen is an essential building block for the entire body, from skin to gut, and more. In boys the diagnosis is limited to those who develop pubic hair or axillary hair before the age of 9. There is a striking sexual dimorphism in the circulating concentration of leptin at birth, at which time females have higher levels than males, and again in late puberty and adulthood.
Size and appearance of the vagina
These changes can be timed and measured. Apart from SRY, a number of autosomal and X-chromosome-linked genes have been identified and have a critical role in male or female sex determination, the testis- and ovary-determining cascades Roberts et al. When baby boys are born, the foreskin tissue is fused to the glans of the penis. By the mm crown-rump stage, male and female fetuses can be distinguished by inspection of the external genitalia; in the male, the urethral folds have fused completely in the midline to form the cavernous urethra and corpus spongiosa by the 12th to 14th weeks of gestation.