Endocrine Abstracts

Prolactinomas are the most common pituitary lesion, and respond well to treatment with dopamine agonists. It presents a diagnostic and therapeutic challenge when there is concurrent psychosis, the treatment of which involves dopamine antagonists. A 69-year-old post-menopausal lady with schizophrenia, on olanzapine 5mg ever, evening, presented with unstead, gait. MRI brain scan showed a 3.3 x 1.8 x 2.4 cm pituitary macroadenoma with optic chiasm indentation. Visual field testing showed bitemporal hemianopia. There was marked hyperprolactinemia, low free thyroxine with inappropriatel, normal TSH, inappropriate low FSH and LH for post-menopausal state. Her ACTH stimulation test was robust. She was diagnosed with macroprolactinoma complicated by visual involvement, central hypothyroidism, central hypogonadism. After discussion with psychiatry and neurosurgery olanzapine was stopped and she started on bromocriptine and levothyroxine. She developed giddiness with bromocriptine, hence we switched to cabergoline 0.25mg/week with gradual dose escalation. Follow up showed improvement in her prolactin and free thyroxine. Repeat MRI demonstrated interval decrease in macroadenoma size (2.7 x 2.2 x 1.7 cm) and reduced mass effect on the optic chiasm with clinical improvement in visual fields. This case illustrates diagnostic pitfalls in hyperprolactinemia. Prolactin should be checked in all pituitary lesions. After excluding high dose hook effect, the degree of prolactin elevation can help differentiate between prolactinoma, stalk effect or drug induced hyperprolactinemia. Antipsychotics may worsen hyperprolactinemia, enhance macroprolactinoma growth, and blunt effect of dopamine agonist treatment. Cessation of her antipsychotics needs to be balanced against risk of psychotic exacerbation. Close psychiatry follow-up and cautious uptitration of dopamine agonists is recommended.