Another nice report of total pituitary enlargement due to the long-standing untreated primary hypothyroidism. Low levels of FT3 and FT4 lead to excessive TRH and TSH production, in turn causing pituitary expansion.
This case is unique as it is found in a child suffering from growth retardation. Proper treatment with thyroid hormone supplementation reversed the illness.
N E J M
A 10-year-old girl presented to the pediatric clinic with headache and poor growth. On examination, her height was below the third percentile and her weight was at the tenth percentile. She had dry skin; testing showed no visual-field deficits.
Laboratory studies showed a TSH level of more than 150 μU per mL, a FT4 level of 0.4 ng/dL, and a PRL level of 63 ng/mL. The results of additional testing, which included the evaluation of levels of morning cortisol, LH, FSH, and IGF-1, were normal.
Head MRI revealed a diffusely enhancing lesion in the sellar region extending to the optic chiasm (Panel A, arrow). A diagnosis of primary hypothyroidism with secondary pituitary hyperplasia was made, and the patient began receiving levothyroxine.
Long-standing untreated primary hypothyroidism can cause pituitary hyperplasia owing to hormonal-feedback mechanisms through the hypothalamic–pituitary–thyroid axis. At 10 months of follow-up, the patient’s headaches had resolved, the thyrotropin level had normalized, and the patient had grown 6 cm in height. Repeated MRI of the head showed resolution of the pituitary enlargement (Panel B).