CASE 1 Tshsecreting Pituitary Adenoma Case Description

A 54-yr-old African-American woman was seen at an urgent care facility because of the recent development of palpitations. When examined, she was noted to have a pulse of 100 bpm. Her thyroid was normal in size, and the rest of the physical examination was normal. Thyroid function tests were as follows: T4 14 |lg/dL, T3RU 43% (25-35), thyroid-stimulating hormone (TSH) 1.6 mU/L. These results were interpreted as indicating that the patient was euthyroid, and she was started on a P-blocker for symptomatic relief. However, one of the physicians in the urgent care center felt that the thyroid function tests were somewhat inconsistent, and called for further advice.

Two weeks later, the patient presented for an evaluation. Since starting on atenolol 50 mg twice daily, her palpitations had resolved. She denied nervousness, tremor, hyper-defecation, insomnia, weakness, shortness of breath, chest pain, or symptoms of ophthal-mopathy. she had not noticed anterior neck discomfort, dysphagia, hoarseness, or neck swelling. she also denied headaches, visual changes, or a personal or family history of thyroid disease.

Her past history was unremarkable except for mild hypertension, controlled with a diuretic. There was no family history of thyroid or autoimmune disease. She was taking no medications other than the diuretic and the atenolol. She was 1 yr postmenopausal and had not taken hormonal replacement therapy (HRT).

On physical exam, pulse 80/min, BP 140/85 mmHg, wt 200 lbs. There was no propto-sis and extraocular movements were full. The thyroid gland was twofold enlarged, firm, and symmetrical. No nodules were appreciated, and a bruit was not audible. The trachea

From: Contemporary Endocrinology: Challenging Cases in Endocrinology Edited by: M. E. Molitch © Humana Press Inc., Totowa, NJ

Fig. 1. Coronal section of a pituitary MRI showing an 11 mm pituitary tumor.

was in the midline and there was no cervical lymphadenopathy. The lungs, heart, abdomen, and extremities were unremarkable. There was no tremor and the skin was warm and dry.

Repeat laboratory testing of thyroid function was as follows: fT4 1.9 ng/dL (n:0.8-1.5), T3 265 ng/dL, TSH 1.6 mU/L. A 24-h radioiodine uptake was elevated at 42% (normal 10-30%). Other tests that were done included: estradiol 4 pg/mL, LH 26 mlU/L (postmenopausal 40-103), follicle stimulating hormone (FSH) 43 mlU/L (postmenopausal 34-96), prolactin 7.8 ng/mL, a subunit 1.5 ng/mL (n:<1.0; <3.6 for postmenopausal women), insulin-like growth factor (IGF)-1 269 ng/mL (90-360), morning cortisol 17 |lg/ dL. Sex hormone binding globulin (SHBG) was 91 nmol/L (n:20-106). A T4 binding panel, which is an electrophoretic analysis of the distribution of radiolabeled thyroxine among serum proteins, was normal. A magnetic resonance imaging (MRI) of the pituitary revealed an 11-mm pituitary microadenoma, which was close to, but did not impinge on the optic chiasm (see Fig. 1). A formal visual field examination was normal. The patient was started on Methimazole (Tapazole) 20 mg/d. One month later, her thyroid function tests were as follows: fT4 1.5 ng/mL, T3 131 ng/mL, TSH 4.6 mU/L. She was referred for neurosurgical evaluation, and underwent transsphenoidal hypophysectomy shortly thereafter. She recovered uneventfully from surgery, and had normal thyroid function off antithyroid drugs. Postoperative testing of the pituitary-adrenal axis showed normal adrenal function. Two years after surgery, on estrogen replacement therapy T4 was 11.4 mcg/dL, T3RU 23% (28-40), FTI 2.7 (1.6-3.7), thyroid stimulating hormone (TSH) 1.1 mU/L.



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