Rapid progression of pituitary hyperplasia in humans with primary hypothyroidism: demonstration with MR imaging.
OBJECTIVE
To use magnetic resonance (MR) imaging to evaluate the morphologic changes of the pituitary gland during the development of hypothyroidism.


METHODS
Fourteen patients who had undergone thyroidectomy were evaluated before radioactive iodine 131 therapy. In each patient, MR imaging and measurement of serum hormone levels were performed twice: 5 weeks before 131I treatment as the "euthyroid state" with thyroid hormone supplementation and on the day of 131I treatment as the "hypothyroid state" after a 3-week depletion of thyroid hormone supplements. Nine healthy volunteers also underwent MR imaging twice at an interval of 5 weeks. Pituitary volume and the relative signal intensity ratio of the anterior pituitary to the pons were measured. The shape and signal intensity of the pituitary gland were also visually assessed. The paired Student t test was used to evaluate the significance of the data. A P value less than .05 indicated a statistically significant difference.


RESULTS
The patients had significantly larger pituitary volume in the hypothyroid state than in the euthyroid state both quantitatively (P < .001) and visually. No significant differences were found in the relative signal intensity ratios of the anterior pituitary to the pons. In healthy volunteers, no significant differences in pituitary volumes or signal intensity were found between the two MR images.


CONCLUSIONS
Rapid progression of hyperplasia of the anterior pituitary may occur with acute development of hypothyroidism.
Shimono
T
T
Department of Nuclear Medicine and Radiology, Faculty of Medicine, Kyoto University, Japan. shimono@kuhp.kyto-u.ac.jp
Hatabu
H
H
Kasagi
K
K
Miki
Y
Y
Nishizawa
S
S
Misaki
T
T
Hiraga
A
A
Konishi
J
J
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D018450:Disease Progression; D005260:Female; D006801:Humans; D006965:Hyperplasia; D007037:Hypothyroidism / Q000150:complications*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D010902:Pituitary Gland / Q000473:pathology*; D011446:Prospective Studies; D013997:Time Factors