Related case report: in vivo suppression of thyrotropin by 9-cis retinoic acid.

Treatment of a 48-year-old woman with advanced cervical cancer with the synthetic vitamin A derivative, 9-cis retinoic acid (9cRA), resulted in thyroid-stimulating hormone suppression without clinical evidence of thyrotoxicosis, which resolved spontaneously when the drug was withdrawn. 9cRA, which is a pan-retinoid (RAR and RXR) agonist, has previously been implicated in induction of interactions between the thyroid receptor and the retinoid receptor, RXR, with endocrine target organ specificity. Furthermore, 9cRA has been shown to down-regulate thyroid-stimulating hormone messenger RNA in a pituitary-specific fashion in a murine model, a finding consistent with the pituitary-restricted thyrotoxicosis observed in our patient. This is the first reported case of thyroid-stimulating hormone suppression by 9cRA and suggests that patients receiving this agent should be monitored for pituitary and thyroid function abnormalities.