Antipsychotic Medication Use Delays Diagnosis of Acromegaly

Background: Elevated prolactin level from use of antipsychotic medication masked the diagnosis of acromegaly. Clinical Case: A 29-year old woman presented with galactorrhea, metrorrhagia, menorrhagia, 50 lb. weight gain, hirsutism, insomnia, and breast engorgement for one year. She was evaluated by gynecology and treated with a combination estrogen/progesterone pill, and then switched to a patch. For several years she had been on haloperidol and various phenothiazine medications for paranoid schizophrenia. Initial evaluation included elevated prolactin level of 94.46 ng/ml (5.2-26.25 ng/mL). Differential diagnosis of PCOS versus medication induced hyperprolactinemia was considered. Patient was started on metformin and referred to nutrition for weight management. MRI scan ordered by her primacy care physician revealed a 13 x 12 x 10 mm pituitary mass with intrinsic mixed density and homogenous enhancement. Visual field testing revealed no deficits. On further testing: IgF-1 432 ng/ml (53-331 ng/ml), TSH 0.85 uIU/mL (0.35-4.94 IUI/ml), ACTH 22 pg/mL (6-50 pg/ml), cortisol 7.7 ug/dl (4.3-22.4 mcg/dl). Differential diagnosis of stalk compression versus functioning adenoma was considered and cabergoline was initiated after she was seen by neurosurgery and declined surgical intervention. She was noncompliant with cabergoline. Surveillance over next two years showed no increase in tumor size on MRI or change in hormone levels. She was then lost to follow up for a year and presented with increased diaphoresis and swelling of her hands. Prolactin three years after diagnosis decreased to 50.59 ng/mL and IgF-1 to 639 ng/ml. She was then referred to endocrinology. Oral glucose tolerance test did not suppress growth hormone below 1.9 ng/ml. Her cortisol suppressed to 0.1 mcg/dl with 1 mg dexamethasone. A diagnosis of Acromegaly was confirmed. She was referred for neurosurgical evaluation and scheduled for transsphenoidal hypophysectomy. She failed to arrive for scheduled surgery. Repeat MRI five years after diagnosis showed a 13 x 16 x 20 mm pituitary adenoma with IgF-1 level of 1011 ng/ml. Octreotide LAR 20 mg monthly was initiated. After two months of injections: prolactin 69.36 ng/ml, IgF-1 778 ng/ml. Repeat visual field testing showed mild constriction in the superior and inferior temporal fields. Patient was scheduled for MRI and surgical procedure but was lost to follow-up. Conclusion: Elevation in prolactin levels in conjunction with antipsychotic medications and diagnosis of schizophrenia masked the early diagnosis of Acromegaly in this patient.