Primary hypothyroidism and pituitary enlargement. Radiological evidence of pituitary regression.

A patient with primary hypothyroidism and pituitary gland enlargement was studies extensively before and after replacement therapy with levothyroxine sodium. She had evidence of bulging of the diaphragma sellae and increased serum prolactin levels. Thyroid replacement therapy resulted in regression of the pituitary size, as shown on pneumoencephalogram, but mildly elevated serum prolactin levels persisted.