The application of fine-needle aspiration (FNA) to the evaluation of the thyroid nodule has greatly enhanced the ability of the clinician to appropriately select patients for thyroidectomy. However, despite extensive experience with thyroid FNA, the cytological distinction of benign from malignant follicular neoplasia remains problematic. As a result, most patients with FNA findings of a follicular neoplasm are referred for thyroidectomy. The goal of the present study was to develop clinical criteria capable of predicting malignancy in patients with an FNA diagnosis of follicular neoplasm. Among 1121 patients undergoing thyroid FNA at two large teaching centers during the period 1990 to 1995, 149 patients had cytological findings consistent with a follicular neoplasm. Among 103 patients referred for thyroidectomy, 22 (21%) were found to have a malignancy in the biopsied nodule. Among patients subjected to thyroidectomy, the risk of malignancy was significantly higher when follicular neoplasia was present in a male (43% vs. 16% for females, p = 0.007), when the nodule was greater than 4 cm to palpation (40% vs. 13% for nodules less than 4 cm, p = 0.03), or when the nodule was judged to be solitary by palpation (25% vs. 6% for a dominant nodule in a multinodular goiter, p = 0.02). Bayesian analysis of the data reveals that after an FNA showing a follicular neoplasm, the risk of malignancy in males with large nodules was nearly 80%, compared with a rate of only 3% in females with small nodules. These results suggest that clinical features including gender, nodule size, and character of the gland by palpation can be systematically integrated into the decision analysis, thereby improving the selection of patients for surgical referral.

Propylthiouracil discontinued 4-7 days before radioiodine dosing is associated with a significant increase in the failure rate of a single dose of radioiodine. Discontinuation of the propylthiouracil for at least a week before radioiodine administration is associated with a higher, although not statistically significant, radioiodine failure rate. In patients that require treatment with propylthiouracil before radioiodine therapy, a higher total serum thyroxine level at diagnosis is associated with an increased rate of radioiodine failure. Consideration should be given to increasing empirically the dose of radioiodine administered to Graves' disease patients that have received propylthiouracil within a week of radioiodine administration in an effort to decrease the radioiodine failure rate to an acceptable level.

These data suggest that following BPD, secondary hyperparathyroidism attributed to hypocalcemia results from malabsorption of vitamin D. However, we cannot exclude the possibility of concurrent calcium malabsorption with vitamin D malabsorption.

Extended Antarctic residence (AR) is associated with an increase in serum TSH, a decrease in free T(4), and an increase in T(3) production and clearance. It is not clear whether these adaptations reflect changes in clearance alone or whether intrinsic thyroidal synthetic activity also changes. Thyroglobulin (Tg) secretion is an independent marker of intrinsic thyroid activity whose kinetics are independent of those of T(3) and T(4). In this study we examined changes in Tg levels in healthy subjects before and during AR and their responses to thyroid supplementation to help determine whether alterations in thyroid activity, and not just kinetics of clearance, underlie the changes seen with the polar T(3) syndrome. In cohort 1, we compared measurements of TSH and Tg in 12 subjects before deployment and monthly for 11 months during AR. In cohort 2, we compared the same measurements in 12 subjects monthly for 11 months of AR. Subjects were randomized to receive either placebo or levothyroxine in cohort 1 for 7 months and in cohort 2 for 11 months. Tg increased over baseline during the first 4 months of AR by 17.0 +/- 4.6% and after 7 more months by 31.7 +/- 4.3% over baseline in the placebo group of both cohorts (P < 0.0002). When L-T(4) was taken, Tg returned to a value not different from baseline (4.5 +/- 3.9%). The percent changes from baseline in serum TSH and Tg during AR were highly correlated (P < 0.00003) in the placebo group for both cohorts. The rise in Tg with TSH and the reduction in Tg with L-T(4) provide evidence of target tissue response to TSH and further confirm the TSH rise as physiologically significant. The results also suggest that the adaptive changes in thyroid hormone economy with AR reflect TSH-dependent changes in thyroid synthetic activity, which may help explain a portion of the increases in T(3) production found with AR.

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