Pituitary Hyperplasia Secondary to Primary Hypothyroidism Mimicking a Macroadenoma With Optical Chiasm Compression

Background: A long term untreated primary hypothyroidism can stimulate thyrotropes proliferation, leading to pituitary hyperplasia. This condition is known as pituitary hyperplasia secondary to primary hypothyroidism (PHPH). It is a rare condition that mimics pituitary adenoma and can achieve large proportions with optic chiasm compression. A misdiagnosis may be catastrophic, and a pituitary resection wrongly performed. Clinical Case: A 25-year-old woman with a medical history of delayed neuro psychomotor development and epilepsy due to congenital CNS malformation had a Brain MRI performed for epilepsy follow-up three years earlier. At that time, neuroimaging had shown a pituitary enlargement, and laboratory data were diagnostic of severe primary hypothyroidism with TSH of 290.6 uUI/mL (normal range 0.4 to 4.5 uUI/mL) and T4L