I think I answered this elsewhere but here is my answer again
This is premature adrenarche, the early production of the male hormones from the adrenal glands, when they are produced early or in excess it is important to rule out abnormal reasons. One important cause that is rare and often screened for at birth is congenital adrenal hyperplasia, this is a block in the enzymes that the adrenal glands make and there is a build up of the male hormones that then cause the hair to become coarse and curly in the pubic and axillary area and cute baby sweat to change to body odor. There is a nonclassical kind that may not show till later after birth due to an incomplete block, this needs to be ruled out, if all is well and there is just an early blip of these normally occuring hormones then they can monitor her closely to be sure that things do not advance to stimulate the pituitary to trigger the female hormones associated with early puberty as we know it.
Your doctor does need to refer you to see an endocrinologist and labs are important to get done as well as consideration of an ultrasound of the adrenal gland.
is the hair fine and light colored or is it dark and more like adult hair? could just be regular body hair that everyone has.
no, this is not regular body hair. this is coarse black hair. Regardless, infants do not have genital hair normally. the doc thinks its abnormal since he wants us to see an endo. I just dont know if this is something that will resolve spontaneously if it should be treated. Some lit out there says that the hair falls out eventually.
you need to go to the specialtist because he needs to role out seriuos causes like tumor, early or premature adenarchy.When my daugther was 4 or 5 months i saw a large dark course pubic hair, the endo saw her and was performed a lots lab , also a bone age(hand RX) ,thanks God everything is ok, the doctor told me maybe an hereditary thing because my mom had the same, now she is 2 and she continuos seeing the endo for bone age and labs.
good luck to you and your son.
go to the doctor right away to make sure that everything is ok or for an adequate treatment.