Puberty is a cascade of events involving several years during which the secondary sexual characteristics develop to maturity and menstruation is established. The time of onset of menstruation, varies with race and family, but the average for most girls is from 11-13 years of age. The early puberty seen in developed countries is attributed to improved nutritional status and genetic diversity. Until puberty, the hypothalamus and the anterior pituitary gland are under an inhibitory influence when at the appropriate age, this inhibition is gradually withdrawn and the hypothalamus starts secreting GnRh in a pulsatile manner, initially during sleep, and later throughout 24 hours.
Under the stimulus of GnRh, the anterior pituitary gland releases FSH and later LH, as well as the growth promoting hormone. This growth promoting hormone causes a spurt in the height. The ovaries respond by secreting estrogen which is responsible for breast development (Thelarche), female axillary hair growth (Adrenalarche). This hormone also causes proliferation of endometrium and brings about menstruation. The initial cycles may be irregular and anovulatory due to inadequate follicular maturation. Later, the cycles become regular and ovulatory.
True precocious puberty is the appearance of appropriate secondary sexual characteristics before the age of 8 in girls. The occurrence is due to premature activation of intact hypothalamus-pituitary-ovarian axis. It is however advisable to investigate to rule out other causes such as tumors in the brain, post inflammatory conditions such as meningitis and encephalitis, hormone secreting ovarian tumors and tumors of the adrenal gland.
This may be familial or idiopathic. The delay in puberty causes anxiety in the parents and the girl concerned. The absence of menses in presence of normal growth and secondary sexual characteristics is an ominous sign and suggests the possibility of absence of uterus. A visit to a gynecologist is always advisable.