Idiopathic Hyperprolactinemia Presenting as Polycystic Ovary Syndrome in Identical Twin Sisters: A Case Report and Literature Review

This case report describes 15-year-old identical twin sisters, who presented to us with features of polycystic ovary syndrome (PCOS). A biochemical workup revealed hyperinsulinemia and androgen excess with elevated prolactin levels. The possible etiologies for hyperprolactinemia were excluded with a detailed evaluation and it was labeled as idiopathic. Considering the fact that androgen excess could be caused by either insulin resistance or hyperprolactinemia, we decided to treat one sister with insulin sensitizer metformin and other with dopamine agonist cabergoline. While cabergoline treatment resulted in normalization of prolactin levels and androgen excess, no significant biochemical or clinical improvement occurred with metformin treatment. Hyperprolactinemia was therefore considered to be the cause of androgen excess in both and cabergoline therapy initiated in the other sister as well. Through the report, we conclude that diagnosis of PCOS should be made only after exclusion of alternative causes like hyperprolactinemia and detailed evaluation should be sought for any significant, unexplained prolactin elevation. Although rare, hyperprolactinemia can lead to androgen excess by increasing adrenal androgen secretion, which improves with dopamine agonist therapy.