Ovulation induction aims to achieve repeated unifollicular ovulation in the correction of anovulatory infertility, the commonest cause of which is polycystic ovary syndrome (PCOS). PCOS is associated with insulin resistance, particularly in those who are overweight. Thus, strategies to achieve weight loss and improve insulin sensitivity, including the use of drugs such as metformin, enhance reproductive function. Therapies to induce ovulation first involve the use of the anti-oestrogen clomiphene citrate. Then, for those who fail to ovulate in response to clomiphene citrate, the principal options include parenteral gonadotrophin therapy or laparoscopic ovarian diathermy. The main causes of anovulatory infertility are PCOS (in approximately 80% of cases), hyperprolactinaemia (5%) and hypogonadotrophic hypogonadism (HH, 5%). Premature ovarian failure, which may be preceded by incipient ovarian failure or ‘resistant ovary syndrome’, accounts for approximately 4% of cases, but can only be treated by oocyte donation. Other, less common causes, include hypopituitarism (<1%).
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