Androstenedione is a steroid hormone secreted by the adrenal glands, ovaries and testicles. It is responsible for the onset of sexual differentiation in males and development of male secondary sexual characteristics after the onset of puberty, including, deepening of voice, growth of facial hair, etc. Excess of androstenedione may result in ambiguous external genitalia (infants external genitals do not appear to be clearly either male or female), hirsutism (abnormal growth of facial hair in females), abnormal menstrual cycles in girls and precocious puberty (puberty before age of 9) in boys. Elevated levels are associated with adrenal cancer, some ovarian and testicular tumors, adrenocortical tumors and congenital adrenal hyperplasia.