Endocrine Abstracts

Introduction: Giant prolactinomas (diameter >4 cm) account for less than 5% of all prolactinomas and are usually associated with markedly elevated prolactin (PRL) levels. Despite their benign nature, these tumors can be invasive, potentially leading to mass effect symptoms in affected patients.

Case Report: We report a case of a 40-year-old male admitted to the emergency department with a one-week history of headaches, right palpebral edema, and ptosis of the right eye. He had a prior medical history of idiopathic peripheral facial paralysis and was not taking any medication. Upon examination, bitemporal hemianopsia with a deficit of the superior right eye field was evident. A head CT showed a large expansive lesion (41x58x63mm) centered to the sella turcica lateralized to the right side with clivus erosion and invasion of the right carotid canal and foramen oval. The patient was started on dexamethasone and was admitted to the Neurosurgery ward. Laboratory tests showed a PRL of 26,623 ng/ml, TSH 1.54 µU/ml with fT4 10.3 pmol/l (12-22), follicular stimulating hormone (FSH) 1.82 IU/l, luteinizing hormone (LH) 2.36 IU/l, total testosterone 70 ng/dl (249-836), insulin-like growth factor 1 (IGF-1) of 212 ng/ml. He initiated cabergoline 2.5 mg/week, levothyroxine 50 µg/day and switched dexamethasone to hydrocortisone. After discharge, an ambulatory corticotroph axis evaluation ruled out adrenal insufficiency. Three months after starting cabergoline, prolactin levels decreased to 520 ng/ml and testosterone improved to 280 ng/dl. Pituitary MRI confirmed an infiltrative sellar lesion, demonstrating invasion into the cavernous sinus and a suprasellar extension reaching the optic chiasm, with a reduction in size compared to the initial CT scan (27×18 mm). Headaches and ptosis of the right eye lid also improved significantly. The patient continued cabergoline treatment, experiencing a progressive decrease in prolactin levels and further radiological improvement. No side effects were reported. Genetic studies for MEN1 and AIP yielded negative results.

Conclusion: Giant prolactinomas can present as invasive masses giving rise to compressive symptoms such as visual field abnormalities. It is crucial to assess the hypothalamic-pituitary axis for potential hypopituitarism and treatment should be promptly initiated. In this case we highlight that despite its clinical aggressiveness, medical management can be a successful therapeutic option. Close monitoring through imaging and laboratory assessments is essential to evaluate treatment response.