MON-LB49 Atypical Presentation for a 5.5-cm Macroprolactinoma: Unilateral Visual Loss and Only Partial Hypopituitarism; Asymptomatic Hypogonadism

Background: Macroprolactinoma is an uncommon pituitary tumor which presents mainly in males. The usual presentation is headache, bitemporal hemianopia, and signs/symptoms of hypogonadism. Ours is a case report of 5.5 –cm macroprolactinoma presented with unilateral optic nerve atrophy and asymptomatic hypogonadism. Clinical case: A 50-year-old male with past medical history of type 2 diabetes mellitus and essential hypertension presented with progressive blurred vision of the left eye for 6 months. He was able to perceive color but had difficulty reading. There was occasional headache with left periorbital pain. He was seen by an optometrist and was found to have left optic disc atrophy with suspicion of glaucoma. Subsequent visual field test showed entire left and right superior temporal loss. MRI of the pituitary showed 5.5 x 5.6 x 5.3 cm enhancing mass centered in the sellar/suprasellar region. There was significant mass effect with compression of the optic chiasm, temporal lobe and brainstem. The patient reported mood changes, normal libido, but loss of morning erection. He has family history of pituitary macroadenoma with left optic nerve compression. On physical examination, there were left visual field defect and decreased visual acuity. There were no signs of Cushing’s syndrome, hypothyroidism, acromegaly, or hypogonadism. Laboratory tests showed prolactin of >200 ng/ml and 16,610 ng/ml after dilution (male <13), total testosterone 92 ng/dl (240-950) and free testosterone 1.20 mg/dl (4.26-16.40). Surprisingly, other pituitary hormones were normal: AM cortisol 20.3 µg/dl (6-27), GH 0.24 ng/ml (0.01-0.97), IGF-1 58 ng/ml (40-259), FSH 4 IU/l (1-18), LH 3 IU/l (1.3-9.6), TSH 1.38 µIU/ml (0.34-3), and free T4 0.8 ng/dl (0.6-1.6). The patient underwent surgery with partial resection. Pathology revealed lactotroph adenoma. Postoperative prolactin level was 11,900 ng/ml. Medical treatment with cabergoline 0.25 mg twice weekly has been started. Conclusion: Even though profoundly hypogonadal by labs, the presentation for this 5.5-cm prolactinoma was acute vision loss. The highly elevated prolactin level correlates with the size of macroadenoma. The typical presentation of local mass effect is bitemporal hemianopia, but in our case the patient presented with unilateral optic nerve atrophy. Despite a 5.5-cm lesion, there is partial hypopituitarism; hypogonadism. Based on the size, one would have expected panhypopituitarism. Given a family history of macroadenoma, there might be genetic predisposition. Molecular testing is planned.