Why is puberty delayed in girls?

1. Hypothalamic pituitary disease

The lack of sexual development is due to hypothalamic or pituitary dysfunction, which manifests as low gonadotropin hypogonadism. This dysfunction may be caused by tumors, infections, injuries or congenital defects, or by various other reasons that affect the secretion of GnRH or its pulse secretion rhythm. The main central nervous system tumors include craniopharyngioma, pinealoma, ectopic pinealoma, germ cell tumor and prolactinoma, and other central nervous system diseases may be central nervous system infection, injury or congenital malformation. There is a condition called isolated gonadotropin deficiency, in which the patient only lacks gonadotropin without abnormalities in growth hormone or other pituitary hormones. The stature is not short, because the low level of sex hormones slows down the closure of the epiphysis, allowing the long bones to grow. The patient has long limbs, large finger span, and a reduced ratio between the upper and lower body.

Kallmann syndrome is a relatively common isolated gonadotropin deficiency, with no sexual development at puberty, often accompanied by olfactory disorders and other malformations. The disease is a heterogeneous genetic disease that can be autosomal dominant, autosomal recessive or X-linked. Due to different inheritance patterns, there are many types of Kallmann syndrome.

Severe systemic and chronic wasting diseases, malnutrition, etc. can all lead to delayed puberty due to functional gonadotropin deficiency. Hypothyroidism and Cushing's disease are also often associated with delayed puberty. Anorexia nervosa is a functional hypogonadotropinemia, which is common in girls who are determined to lose weight or are mentally stressed. Because they cannot eat normally, they suffer from severe low weight, fear of cold, undeveloped sexual characteristics, primary amenorrhea or secondary amenorrhea. Anorexia nervosa can lead to delayed puberty if it occurs in the prepuberty period. Some athletes or ballet dancers who undergo high-intensity training have too little body fat due to their high amount of exercise, so their puberty and menarche are later than girls of the same age. Prepubertal hyperprolactinemia can cause delayed puberty, but it is relatively rare.

2. Ovarian disease

Sexual characteristics are not developed due to ovarian hypoplasia or dysfunction. Due to the poor ovarian function, the ovaries cannot synthesize and secrete enough sex hormones, which interferes with the negative feedback regulation of the pituitary gland and hypothalamus, increases the secretion of gonadotropin, leads to increased FSH and LH levels, and low E2 levels, so it is also called hypergonadotropic hypogonadism. This situation is often seen in congenital developmental abnormalities and often manifests as sexual immaturity. There is a kind of congenital gonadal dysgenesis, also known as Turner syndrome, which is a congenital disease with abnormal number or structure of X chromosomes. Its typical karyotype is 45, X or other variant forms. Children with ovarian hypoplasia and sex hormone deficiency have undeveloped sex characteristics and are in a sexually immature state. In addition, there is often a group of physical abnormalities, such as short stature, neck webs, multi-faceted nevi, barrel chest, elbow valgus, etc., as well as multiple malformations of internal organs. Hypergonadotropic hypogonadism is also seen in 46,XX and 46,XY simple gonadal dysgenesis, which also manifests as sexual immaturity. Ovarian removal in childhood or damage to ovarian function due to radiotherapy or chemotherapy of the ovarian area can affect puberty development.