Long-Term Follow-Up Over 16 Years for Pituitary Hyperplasia Due to Primary Hypothyroidism With Positive Thyroid Stimulation Blocking Antibody: A Case Report

Primary hypothyroidism is a known risk factor for pituitary hyperplasia, which develops symptoms due to compression of the optic chiasma and increased intracranial pressure. As pituitary hyperplasia is known to improve after levothyroxine replacement therapy, there are no reports of a long clinical course of pituitary hyperplasia due to primary hypothyroidism. We describe a case of follow-up over 16 years for pathologically diagnosed pituitary hyperplasia due to primary hypothyroidism with positive thyroid stimulation blocking antibody. Repeated enlargement and shrinkage were confirmed, but observations also suggested that the pituitary gland did not always return to normal size.