Breastfeeding typically prolongs postpartum lactational amenorrhoea, and the duration of amenorrhoea varies depending on how often a woman breastfeeds. Due to this reason, breastfeeding has been advocated as a method of family planning, especially in developing countries where access to other methods of contraception may be limited. Diseases of the thyroid
Disturbances in thyroid hormone regulation has been a known cause of menstrual irregularities, including secondary amenorrhea.Patients with hypothyroidism frequently present with changes in their menstrual cycle. It is hypothesized that this is due to increased TRH, which goes on to stimulate the release of both TSH and prolactin. Increased prolactin inhibits the release of LH and FSH which are needed for ovulation to occur.Patients with hyperthyroidism may also present with oligomenorrhea or amenorrhea. Sex hormone binding globulin is increased in hyperthyroid states. This, in turn, increases the total levels of testosterone and estradiol. Increased levels of LH and FSH have also been reported in patients with hyperthyroidism. Hypothalamic and pituitary causes
Changes in the hypothalamic-pituitary axis is a common cause of secondary amenorrhea. GnRH is released from the hypothalamus and stimulates the anterior pituitary to release FSH and LH, which in turn stimulate the ovaries to release estrogen and progesterone. Any pathology in the hypothalamus or pituitary can alter the way this feedback mechanism works and can cause secondary amenorrhea.Pituitary adenomas are a common cause of amenorrhea. Prolactin secreting pituitary adenomas cause amenorrhea due to the hyper-secretion of prolactin which inhibits FSH and LH release.
Gonadal dysgenesis, often associated with Turner syndrome, or premature ovarian failure may also be to blame. If secondary sex characteristics are present, but menstruation is not, primary amenorrhoea can be diagnosed by age 16.Evaluation of primary amenorrhea begins with a pregnancy test, prolactin, FSH, LH, and TSH levels. Abnormal TSH levels prompt evaluation for hyper- and hypo-thyroidism with additional thyroid function tests. Elevated prolactin levels prompt evaluation of the pituitary with an MRI to assess for any masses or malignancies. A pelvic ultrasound can also be obtained in the initial evaluation. If a uterus is not present on ultrasound, karyotype analysis and testosterone levels are obtained to assess for MRKH or androgen insensitivity syndrome. If a uterus is present, LH and FSH levels are used to make a diagnosis. Low levels of LH and FSH suggest delayed puberty or functional hypothalamic amenorrhea. Elevated levels of FSH and LH suggest primary ovarian insufficiency, typically due to Turner syndrome. Normal levels of FSH and LH can suggest an anatomical outflow obstruction. Secondary amenorrhea
Secondary amenorrheas most common and most easily diagnosable causes are pregnancy, thyroid disease, and hyperprolactinemia. A pregnancy test is a common first step for diagnosis.Similar to primary amenorrhea, evaluation of secondary amenorrhea also begins with a pregnancy test, prolactin, FSH, LH, and TSH levels. A pelvic ultrasound is also obtained. Abnormal TSH should prompt a thyroid workup with a full thyroid function test panel. Elevated prolactin should be followed with an MRI to look for masses.