DIAGNOSIS AND MANAGEMENT OF THE AUTONOMOUSLY FUNCTIONING THYROID-NODULE - THE WALTER-REED-ARMY-MEDICAL-CENTER EXPERIENCE, 1975-1994

In order to characterize the clinical and laboratory features of auton omously functioning thyroid nodules (AFTNs), and to assess optimal dia gnosis and management of patients with this disorder, we performed a r etrospective analysis of 49 such patients over a 22-year period encomp assing January 1975 to November 1996. The following data were analyzed : thyroid hormone levels, thyroid scintiscan, radioiodine uptake, fine -needle aspiration biopsy, triiodothyronine (T-3) suppression testing, thyrotropin-releasing hormone (TRH) stimulation test, and thyroid ult rasound. Clinical outcomes assessed included persistent hyperthyroidis m, hypothyroidism, and nodule shrinkage after treatment, or in patient s followed without definitive therapy, nodule growth, spontaneous dege neration, and progression to hyperthyroidism. Biochemical hyperthyroid ism, often subclinical, was found in 73.5% of patients at presentation and in an additional 24.4% of patients during subsequent follow-up. T he introduction of sensitive thyrotropin (TSH) testing during the peri od of study resulted in a decrease in the use of the T-3-suppression t est and TRH stimulation test from 100% and 20%, respectively, in the p eriod from 1976-1980, to 4% each in the period from 1991-1996. T-3-thy rotoxicosis occurred in 12.2% of patients. Thyrotoxicosis at any time during the course of follow-up was positively correlated with nodule s ize at diagnosis. Definitive therapy, used in 42.8% of patients, consi sted of radioiodine ablation (38.1%) or thyroidectomy (61.9%). No pati ent had recurrence of thyrotoxicosis after definitive therapy, but 25% became hypothyroid. During follow-up for a mean of 30.9 months, nodul es enlarged in 25% of patients overall, or 33% of patients not receivi ng definitive therapy. Cystic degeneration was documented in 26.5% of patients, although this change rarely reversed subclinical hyperthyroi dism. The diagnosis of an AFTN requires a demonstration of TSH-indepen dent nodular hyperfunction. The introduction of sensitive TSH assays h as simplified the evaluation of AFTN patients and revealed a high prev alence of subclinical thyroid hyperfunction in this disorder. In view of current increased awareness of adverse consequences associated with subclinical hyperthyroidism and the rarity of spontaneous resolution of hyperthyroidism in AFTN patients (despite a propensity for spontane ous hemorrhage), definitive therapy is recommended. Both radioiodine a nd hemithyroidectomy have high cure rates and a low posttreatment inci dence of hypothyroidism.