False positive results using calcitonin as a screening method for medullary thyroid carcinoma.

The role of serum calcitonin as part of the evaluation of thyroid nodules has been widely discussed in literature. However there still is no consensus of measurement of calcitonin in the initial evaluation of a patient with thyroid nodule. Problems concerning cost-benefit, lab methods, false positive and low prevalence of medullary thyroid carcinoma (MTC) are factors that limit this approach. We have illustrated two cases where serum calcitonin was used in the evaluation of thyroid nodule and rates proved to be high. A stimulation test was performed, using calcium as secretagogue, and calcitonin hyper-stimulation was confirmed, but anatomopathologic examination did not evidence medullar neoplasia. Anatomopathologic diagnosis detected Hashimoto thyroiditis in one case and adenomatous goiter plus an occult papillary thyroid carcinoma in the other one. Recommendation for routine use of serum calcitonin in the initial diagnostic evaluation of a thyroid nodule, followed by a confirming stimulation test if basal serum calcitonin is showed to be high, is the most currently recommended approach, but questions concerning cost-benefit and possibility of diagnosis error make the validity of this recommendation discussible.

Role for postoperative cortisol response to desmopressin in predicting the risk for recurrent Cushing's disease.

UNLABELLED: In the early postoperative period of Cushing's disease patients, desmopressin may stimulate ACTH secretion in the remnant corticotrophic tumour, but not in nontumour suppressed cells. OBJECTIVE: The aim of this study is to evaluate the serum cortisol responses to desmopressin after pituitary surgery, establishing an optimal cut-off for absolute increment (Delta) of serum cortisol (F) suitable to predict recurrence risk. DESIGN: Retrospective case record study. PATIENTS: Fifty-seven Cushing's disease patients submitted to pituitary surgery and desmopressin stimulation in the early postoperative with a long-term follow-up (20-161 months) were studied. METHODS AND MEASUREMENTS: Serum cortisol levels after desmopressin test (10 microg i.v.) 15-30 days after adenomectomy were used to determine DeltaF (absolute increment of F: F peak - F baseline). Sensitivity and specificity of DeltaF were calculated and a ROC curve was performed to establish an optimal cut-off for DeltaF to predict recurrence risk. RESULTS: Fifteen patients had immediate postoperative failure (basal F > 165 nmol/l; 6 microg/dl) and one patient was lost during the follow-up. Forty-one patients achieved initial remission and were followed-up. Five of 11 patients who recurred had DeltaF > 193 nmol/l (7 microg/dl), but none of 30 patients who remained in prolonged remission showed DeltaF > 193 nmol/l after postoperative desmopressin stimulation. CONCLUSIONS: Persistence of cortisol response (DeltaF > 193 nmol/l) to desmopressin in the early postoperative period can help to identify Cushing's disease patients with initial remission who present risk for later recurrence.