Oligoanovulation

Oligoanovulation is a pattern of infrequent or irregular ovulation that leads to irregular menstrual cycles and often infertility. It is a feature of several ovulatory disorders, most commonly polycystic ovary syndrome (PCOS), but it can arise from hypothalamic-pituitary dysfunction, thyroid disease, hyperprolactinemia, obesity, severe weight loss, chronic illness, or certain medications.

In PCOS, disruption of the hypothalamic-pituitary-ovarian axis and insulin resistance contribute to abnormal follicular development and incomplete ovulation, resulting in cycles that are widely spaced and often anovulatory. Other causes include hypothalamic dysfunction from stress, excessive exercise, or low body weight; pituitary or thyroid abnormalities; and elevated prolactin levels.

Clinical features typically include menstrual cycles longer than about 35 days or infrequent menses, with or without signs of hyperandrogenism such as hirsutism or acne. Infertility is common due to the irregular or absent ovulation. Ovulation status can be inferred from cycle history and confirmed by biochemical testing, most commonly a mid-luteal serum progesterone level to assess whether ovulation occurred.

Diagnosis involves excluding or identifying underlying causes. Tests may include measurements of serum prolactin, thyroid-stimulating hormone, and androgens; assessment of ovarian morphology by ultrasound; and documentation of ovulation status through luteal-phase progesterone levels or ovulation tracking. Exclusion of pregnancy is necessary in women of reproductive age.

Management aims to restore regular ovulation and treat underlying conditions. For infertility, lifestyle modification (notably weight loss in overweight individuals) and pharmacologic induction of ovulation with letrozole or clomiphene citrate are common first-line options; gonadotropins or pulsatile GnRH may be used if needed. In PCOS, metformin may be added in selected cases. Non-fertility-related care may include hormonal cycle regulation with combined or progestin-only regimens and management of metabolic risk factors.