Thyroid hormone resistance and pituitary enlargement after thyroid ablation in a woman on levothyroxine treatment.

We report a patient with inappropriate secretion of thyrotropin (TSH) and a pituitary mass. Although she had been treated for biochemical hyperthyroidism with thyroid surgery and radioiodine ablation, she had never complained of specific symptoms or demonstrated signs of overt thyroid dysfunction. On evaluation, she had increased free thyroxine and TSH levels, normal serum glycoprotein alpha-subunit levels, and a significant TSH over-response to exogenous thyrotropin-releasing hormone stimulation. Magnetic resonance imaging with gadolinium enhancement showed a pituitary enlargement with suprasellar extension. An indium In 111 pentetreotide scan showed an abnormal focus of radionuclide accumulation in the pituitary area. Sequencing of the TRbeta gene showed that the patient was heterozygous for a new single nucleotide substitution resulting in the replacement of the normal arginine with a serine at amino acid 320 (R320S). We review the difficulties encountered in establishing a correct diagnosis in patients with inappropriate secretion of TSH in combination with pituitary enlargement. Due to its possible false-negative results, we do not recommend the use of indium In 111 pentetreotide as a tool in the differential diagnosis of inappropriate secretion of TSH.

99MTc-sestamibi as sole technique in selection of primary hyperparathyroidism patients for unilateral neck exploration.

BACKGROUND: Unilateral neck exploration (UNE) is becoming the procedure of choice for treatment of primary hyperparathyroidism (PHPT). The aim of this study was to evaluate the role of (99m)Tc-sestamibi (MIBI) parathyroid scintigraphy as the sole technique in selecting patients for UNE. METHOD: We selected 136 consecutive PHPT patients who had only 1 solitary uptake at a MIBI were for UNE. The technique was a single dual-phase using MIBI and a subtraction technique with (99m)Tc-pertechnetate. Imaging data were correlated with surgical results. RESULTS: In 3 cases, the sestamibi scan was falsely positive, 1 had a contralateral location relative to the uptake, and 2 had multiglandular hyperplasia. Overall, the positive predictive value (PPV) of MIBI for detecting a solitary parathyroid adenoma in patients with 1 solitary uptake was 97.8. Sixteen patients (12%) had evidence of multinodular goiter. Overall, the PPV of MIBI was 98.4% (2 false positive among 120 cases) in patients with no multinodular thyroid disease (MNG) and 93.7% (1 false negative among 16 cases) in patients with MNG. The mean duration of the surgical procedure was 34.17 minutes. Mean hospitalization was 0.6 days. Conversion to bilateral neck exploration was performed in 5 patients. After a period of follow-up of 40 months (range, 6-72 months), the cure rate was 98%. CONCLUSION: Patients with PHPT and unequivocally positive preoperative (99m)Tc-sestamibi can safely be managed with UNE without additional localizing techniques.