<P> Before puberty effects of rising androgen levels occur in both boys and girls . These include adult - type body odor, increased oiliness of skin and hair, acne, pubarche (appearance of pubic hair), axillary hair (armpit hair), growth spurt, accelerated bone maturation, and facial hair . </P> <P> Pubertal effects begin to occur when androgen has been higher than normal adult female levels for months or years . In males, these are usual late pubertal effects, and occur in women after prolonged periods of heightened levels of free testosterone in the blood . The effects include: </P> <P> Growth of spermatogenic tissue in testicles, male fertility, penis or clitoris enlargement, increased libido and frequency of erection or clitoral engorgement . Growth of jaw, brow, chin, nose, and remodeling of facial bone contours, in conjunction with human growth hormone . Completion of bone maturation and termination of growth . This occurs indirectly via estradiol metabolites and hence more gradually in men than women . Increased muscle strength and mass, shoulders become broader and rib cage expands, deepening of voice, growth of the Adam's apple . Enlargement of sebaceous glands . This might cause acne, subcutaneous fat in face decreases . Pubic hair extends to thighs and up toward umbilicus, development of facial hair (sideburns, beard, moustache), loss of scalp hair (androgenetic alopecia), increase in chest hair, periareolar hair, perianal hair, leg hair, armpit hair . </P> <P> Testosterone is necessary for normal sperm development . It activates genes in Sertoli cells, which promote differentiation of spermatogonia . It regulates acute HPA (hypothalamic--pituitary--adrenal axis) response under dominance challenge . Androgen including testosterone enhances muscle growth . Testosterone also regulates the population of thromboxane A receptors on megakaryocytes and platelets and hence platelet aggregation in humans . </P>

What role does the male hormone testosterone play in puberty
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