FRI316 A Rare Case Of Mono-hormonal Silent Prolactinoma

Disclosure: Y. Esaki: None. C. Bheeman: None. I. Shafiq: None. Introduction: Silent pituitary adenomas secrete one or more anterior pituitary hormones or express their transcriptions factors, but do not secrete hormones at a clinically relevant level. Silent lactotroph adenomas are rare and often encountered as mixed somatotroph-lactotroph adenomas. Mono-hormonal silent lactotroph adenomas are exceedingly rare with the prevalence of 0.6-1.65% with most belonging to the sparsely granulated subtype. Clinical Case: A 32-year-old male presented with right visual problem over the last 7 months. Evaluation by Ophthalmology revealed trace afferent pupil defect of the right eye and bitemporal hemianopsia. MRI head showed an enhancing mass in the sellar and suprasellar regions collectively measured 2.5 x 2.0 x 1.8 cm, which upwardly displaced and distorted the optic chiasm. Biochemical workup showed normal prolactin 8.1 ng/ml (2.6-13.1) and unremarkable other pituitary hormone levels including ACTH 26 pg/ml (7-63), cortisol 16.6 ug/dl (6.7-22.6), growth hormone 0.08 ng/ml (0.00-2.47), LH 4.1 mIU/ml (1.2-8.6), FSH 5.8 mIU/ml (1.3-19.3), estradiol 27.9 pg/ml (15.0 - 31.5), total testosterone 527 ng/dl (240-950), free testosterone 16.1 ng/dl (4.85-19.0), SHBG 23 nmol/L (10-80), TSH 3.34 uIU/ml (0.34-5.60), free T4 0.84 ng/dl (0.58-1.64). He underwent transsphenoidal hypophysectomy. Final pathology showed densely granulated lactotroph, with extensively positive PRL in tumor cells, positive Pit-1 and negative ERa. Patient did well post-operatively. Conclusion: This case illustrates a rare case of a mono-hormonal silent pituitary lactotroph adenoma. The majority of lactotroph adenomas are sparely granulated, so the densely granulated histology shown here makes this case even more rare. Unfortunately, there is no data reported in relation to the association between this histological subtype and the invasiveness of tumor. We need more cases to characterize this subtype of tumor better. Presentation: Friday, June 16, 2023