What is the most common cause of primary amenorrhea?

The most common cause of primary amenorrhea is Turner syndrome, which is a chromosomal condition affecting females characterized by the absence or structural abnormalities of one of the X chromosomes. This disorder can lead to several developmental changes, including ovarian dysgenesis, resulting in a lack of estrogen production and subsequently the failure to initiate normal menstrual cycles.

In Turner syndrome, individuals often present with short stature, webbed neck, and other characteristic physical features. Due to the underdeveloped ovaries, individuals do not experience the hormonal changes necessary for the development of secondary sexual characteristics or menarche, leading to primary amenorrhea.

Other conditions like polycystic ovary syndrome and congenital adrenal hyperplasia are more associated with secondary amenorrhea rather than primary, as they typically occur after a period of normal menstrual cycles. Hyperprolactinemia can lead to amenorrhea, but it is usually a secondary cause, resulting from other underlying issues rather than a primary disorder. Thus, in the context of primary amenorrhea, Turner syndrome stands out as the most prevalent diagnosis.