Editing Anovulation (section)

=== Hypogonadotropic hypogonadism ===
Hypothalamic causes of HA include functional hypothalamic amenorrhea (FHA) and isolated gonadotropin-releasing hormone (GnRH) deficiency.<ref name="FARIDDiamanti-Kandarakis2009" /> Laboratory findings of low serum estradiol and low FSH are associated with the decrease in hypothalamic secretion of GnRH.<ref name="FARIDDiamanti-Kandarakis2009" />

A rare form of HA that presents as primary amenorrhea can be due to a congenital deficiency of GnRH knows as idiopathic hypogonadotropic hypogonadism or, Kallmann syndrome if it is associated with anosmia.<ref name="FARIDDiamanti-Kandarakis2009" /> Infiltrative disease or tumors affecting the hypothalamus and pituitary can result in HA.<ref name="FARIDDiamanti-Kandarakis2009" />

FHA accounts for around 10–15% of all cases of anovulation. Weight loss or [[Anorexia nervosa|anorexia]] can lead to FHA by causing a hormonal imbalance, leading to irregular ovulation (dysovulation). It is possible that this mechanism evolved to protect the mother's health. A pregnancy where the mother is weak could pose a risk to the baby's and mother's health. On the other hand, excess weight can also create ovarian dysfunctions. Dr Barbieri of Harvard Medical School has indicated that cases of anovulation are quite frequent in women with a BMI ([[body mass index]]) over 27&nbsp;kg/m2.