COVID-19 Vaccine-Induced Expansion of Pituitary Adenoma: A Case Report.

A pituitary adenoma is an insidious and slow-growing neoplasm of the pituitary gland. No definitive aggravating factors have currently been reported for pituitary adenoma enlargement. Our case demonstrates that the coronavirus disease 2019 (COVID-19) vaccine may be one of the risk factors aggravating tumor expansion. A 60-year-old woman experienced visual loss in her left eye for three days. Eight days before presentation or five days before visual loss, she received the fourth dose of the COVID-19 vaccine. The visual field showed bitemporal superior quadrantanopic scotoma, prominent on the left side. Neuroimaging revealed pituitary macroadenoma with a compressive effect on the optic chiasm. After diagnosis, endocrine work-up and tumor removal were successfully performed. Her vision and perimetry significantly improved. The COVID-19 vaccine is a candidate factor that might exacerbate pituitary gland enlargement. Additional data are essential to validate and establish the connection between the vaccine and this potential effect.