Hypogonadism may be suspected if puberty is delayed. Pubertal delay may be caused by a normal physiological variant, by primary ovarian insufficiency (Turner syndrome), or reflect congenital hypogonadotropic hypogonadism (HH; genetic) or acquired HH (brain lesions). Any underlying chronic disease like inflammatory bowel disease, celiac disease, malnutrition (anorexia or orthorexia), or excessive physical activity may also result in functional HH. Thus, girls with delayed puberty should be evaluated for an underlying pathology before any treatment, including oral contraception, is initiated. Estrogen replacement is important and natural 17β-estradiol, preferably transdermally, is the preferred choice, whereas the oral route can be used as an alternative depending on patient preference and compliance. Sexual activity is often delayed in the hypogonadal adolescent girl. In the adolescent hypogonadal girl, hormone replacement therapy (HRT) most likely has been initiated at the time she becomes sexually active. If a risk of unwanted pregnancy cannot be ruled out, there is a need to consider contraception. This consideration does not contradict the principles of HRT but can be included as a part of the substitution, e.g. oral contraceptives containing 17β-estradiol or a progestogen intrauterine device combined with continuous 17β-estradiol (transdermal or oral).