Puberty is the biological process in which children undergo physical and sexual maturation so that they attain adult physical characteristics and reproductive capability.
In girls, this involves the primary sexual development of the ovaries and the genitals (uterus, vagina and vulva), secondary sexual development of the breasts, pubic and axillary hair, and acceleration of height and weight growth along with changes in body composition. Thelarche refers to the onset of breast development, menarche to the onset of periods and gonadarche to the onset of mature gonadal function when ovulation (release of the oocyte or egg) first occurs.
The timing of puberty is related to genetic factors (50-80%) and environmental factors with ethnic and geographical differences. Increased weight has led to an earlier onset of puberty and menses in girls but the average age for menarche remains in the twelfth year of life.
The onset of puberty occurs when the central nervous system activates the HPO (hypothalamus-pituitary-ovarian) axis. This allows for release of hormones that stimulate the ovaries to produce oestrogen (oestradiol). This induces breast development, changes in body shape, a growth spurt and then growth plate fusion (in the bones). In late puberty, this hormone secretion becomes a complex loop that is responsible for the mature reproductive menstrual cycle with oocyte development, ovulation and menses, which continue regularly unless pregnancy occurs.
This sequence of events is usually orderly and predictable and the stages of progression are known as the Tanner staging (see Fig 1). The time from onset of breast development to onset of menses is usually two years. Ovarian size on ultrasound is another simple measure for assessing gonadal development. Ovaries have a volume of less than 1.5ml prior to puberty and reach a volume of 4-20ml after menarche.
Disorders of puberty are primarily when puberty occurs too early, too late or not at all. There should be clinical suspicion if the sequence of events fails to progress or is out of the expected order.
Delayed or absent puberty in girls is defined as no pubertal changes by 13years of age. This can be caused by constitutional (familial, chronic illness, malnutrition or excessive exercise), hypothalamic (congenital, vascular, iron excess, trauma, tumours and irradiation), pituitary (congenital, or tumours), gonadal (congenital such as Turners syndrome or acquired such as trauma, removal or chemotherapy) or structural (absent mullerian structures or abnormal septums) issues. These issues need thorough investigation by a specialist and appropriate management.
Early or precocious puberty in girls is defined as signs of puberty that occur before 8years of age. When the normal sequence occurs, with the gonadotropin (LH and FSH) levels seen to be rising early, this is usually central in origin and in 80% of females there is no cause found. Other central causes include surgery, irradiation, infection, tumours and hydrocephalus. Non-central causes are seen when oestradiol levels are raised but the central gonadotropin (LH and FSH) levels are not raised meaning that the source of hormone is from elsewhere in the body. This can occur with congenital adrenal hyperplasia (CAH), McCune Albright syndrome, tumours and exogenous ingestion. Rarely, tumours of the gonads or adrenal glands can produce testosterone and result in significant changes of puberty more commonly seen in the opposite gender.
Other abnormal pubertal events can also occur but are not specifically delayed or early puberty. The early appearance of pubic and axillary hair often accompanied by increased body odour is known as premature pubarche. Abnormal androgen production and CAH needs to be excluded but can usually just be followed. Premature thelarche is the early, isolated onset of breast development with no change in hormonal levels and no evidence of maturation of other genital structures and normal growth patterns. No treatment is required but follow up to ensure normal puberty is recommended. Female hirsutism with the appearance of terminal hair is different to normal secondary sexual hair and needs to be considered in clinical context. If associated with infrequent menses but without virilisation (clitoromegaly, balding, deepening of the voice and lossof female characteristics) and mild elevations in testosterone, the polycystic ovaries or late onset CAH are most likely. If virilisation is present, this usually indicates an adrenal or ovarian tumour and requires urgent investigation.
Specialists involved in evaluating these areas include paediatric endocrinologists and reproductive endocrinologists.