Refers to the absence of menstrual bleeding and may be primary or secondary.

Primary amenorrhea is the absence of menstrual bleeding and secondary sexual characteristics in a girl by age 14 years or the absence of menstrual bleeding with normal development of secondary sexual characteristics in a girl by age 16 years.

Secondary amenorrhea is the absence of menstrual bleeding in a woman who had been menstruating but later stops menstruating for 3 or more months in the absence of pregnancy, lactation, cycle suppression with systemic hormonal contraceptive pills, or menopause.

To have regular menstrual cycles the hypothalamus, pituitary gland, ovaries, and uterus must all be functioning normally.

The hypothalamus stimulates the pituitary gland to release follicle-stimulating hormone (FSH) and luteinizing hormone (LH).

FSH and LH cause the ovaries to produce the hormones estrogen and progesterone.

Estrogen and progesterone are responsible for the cyclical changes in the endometrium, including menstruation.

The hypothalamic central nervous system discharges gonadotropin-releasing hormone (GnRH), which is transported to the anterior pituitary, where it stimulates the gonadotrophs.

FSH stimulate the gonads to synthesize and secrete sex steroids.

Hypothalamus-pituitary-ovarian axis hormone secretion is regulated by a negative feedback on gonadotrophs in the anterior pituitary and by indirect inhibition at the level of the hypothalamus.

Any disruption in this axis may result in amenorrhea.

Hypothalamic dysfunction results in decreased GnRH secretion, which affects the pulsatile release of LH and FSH, causing anovulation.

Functional hypothalamic amenorrhea is characterized by abnormal hypothalamic GnRH secretion, decreased gonadotropin pulsations, low or normal LH concentrations, absent LH surges, abnormal follicular development, low serum estradiol, serum FSH concentrations are usually in the normal range.

Congenital GnRH deficiency leads to low gonadotropin levels and when this occurs with anosmia, it is known as Kallman syndrome.

Kallman syndrome may be associated with midline facial defect, renal agenesis, neurologic deficiency, and is usually an X-linked recessive disorder.

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