Coexistence of TSH-secreting pituitary adenoma and autoimmune hypothyroidism.
OBJECTIVE
TSH-secreting pituitary adenomas account for about 1-2% of all pituitary adenomas. Their diagnosis may be very difficult when coexistence of other diseases masquerades the clinical and biochemical manifestations of TSH-hypersecretion.


METHODS
A 41-yr-old female patient, weighing 56 kg, was referred for evaluation of an intra- and suprasellar mass causing menstrual irregularities. Eight yr before, the patient had been given a diagnosis of subclinical autoimmune hypothyroidism because of slightly elevated TSH levels and low-normal free T4 (FT4). Menses were normal. Despite increasing doses of levo-T4 (L-T4; up to 125 microg/day), TSH levels remained elevated and the patient developed mild symptoms of hyperthyroidism. After 7 yr, the menstrual cycle ceased. Gonadotropins were normal, whereas PRL level was elevated at 70 microg/l and magnetic resonance imaging (MRI) of the hypothalamic- pituitary region revealed a pituitary lesion with slight suprasellar extension. The tumor was surgically removed and histological examinations revealed a pituitary adenoma strongly positive for TSH. Three months after surgery the patient was well while receiving L-T4 75 microg/day and normal menses had resumed. MRI of the hypothalamic-pituitary region showed no evidence of residual tumor. At the last follow-up, 16 months after surgery, serum TSH, free T3 (FT3), and FT4 levels were normal.


CONCLUSIONS
Coexistence of autoimmune hypothyroidism and TSH-secreting pituitary adenoma may cause further delays in the diagnosis of the latter. In patients with autoimmune hypothyroidism, one should be aware of the possible presence of a TSH-secreting pituitary adenoma when TSH levels do not adequately suppress in the face of high doses of L-T4 replacement therapy and elevated serum thyroid hormone levels.
Losa
M
M
Pituitary Unit, Department of Neurosurgery, Istituto Scientifico San Raffaele, Università Vita-Salute, 20132 Milano, Italy. losa.marco@hsr.it
Mortini
P
P
Minelli
R
R
Giovanelli
M
M
D000236:Adenoma / Q000150:complications* / Q000378:metabolism*; D000328:Adult; D001327:Autoimmune Diseases / Q000150:complications*; D005260:Female; D006801:Humans; D007037:Hypothyroidism / Q000150:complications*; D008599:Menstruation Disturbances / Q000209:etiology; D010911:Pituitary Neoplasms / Q000150:complications* / Q000378:metabolism*; D013972:Thyrotropin / Q000378:metabolism*; D013974:Thyroxine / Q000097:blood
D013972:Thyrotropin; D013974:Thyroxine