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Levothyroxine and Potassium Iodide Are Both Effective in Treating Benign Solitary Solid Cold Nodules of the Thyroid

Giacomo L. La Rosa, MD; Lorenzo Lupo, MD; Dario Giuffrida, MD; Damiano Gullo, MD; Riccardo Vigneri, MD; and Antonino Belfiore, MD
[+] Article and Author Information

From the University of Catania, Catania, Italy. Requests for Reprints: Giacomo L. La Rosa, MD, Cattedra di Endocrinologia, Ospedale Garibaldi, Piazza S. Maria di Gesu, 95123 Catania, Italy. Acknowledgments: The authors thank the Cyanamid Italia SpA for providing the potassium iodide tablets; Dr. A. Nastri for his help in the study design; and Drs. C. Regalbuto, L. Sava, V. Freni, M.G. Santonocito, and G. Briguglia for their help in the recruitment and follow-up of patients.


Copyright ©2004 by the American College of Physicians


Ann Intern Med. 1995;122(1):1-8. doi:10.7326/0003-4819-122-1-199501010-00001
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Objective: To determine the effectiveness of levothyroxine and potassium iodide in treating patients with benign solitary cold thyroid nodules.

Design: Randomized controlled study.

Setting: Outpatient clinic at a university hospital.

Patients: 80 patients with solitary solid cold thyroid nodules found to be benign at cytologic examination were randomly assigned to no treatment, suppressive levothyroxine (thyroid-stimulating hormone level, <0.3 mU/L), or low-dose potassium iodide (2 mg every 2 weeks). Seventy patients completed the 1-year study. After 1 year, patients receiving treatment discontinued drug therapy and were re-evaluated 4 months later; patients receiving no treatment were given levothyroxine and were followed for a second year.

Measurements: Nodule volume was measured by ultrasonography at 4-month intervals by an observer masked to treatment assignment.

Results: Mean nodule volume decreased by 40% of the basal volume in the 23 patients receiving levothyroxine (P < 0.001) and by 23% of the basal volume in the 25 patients receiving potassium iodide (P = 0.053). Volume slightly increased in the 22 untreated patients (P = 0.085). A clinically relevant reduction in nodule volume (≥ 50%) was observed in 9 of 23 patients treated with levothyroxine, in 5 of 25 patients treated with potassium iodide, and in none of 22 untreated patients (P = 0.004). Only nodules with a volume of 10 mL or less were reduced; nodules with volumes of 5 mL or less shrank most frequently. Nodule volume did not relevantly increase in treated patients but did increase in 3 of the 22 untreated patients. Drug withdrawal resulted in an increased mean nodule volume (P = 0.004) after 4 months.

Conclusions: Levothyroxine and, to a lesser extent, potassium iodide are effective in arresting the growth or in reducing the volume of benign solitary solid cold thyroid nodules, especially small ones; discontinuation of therapy may result in resumed nodule growth.

Figures

Grahic Jump Location
Figure 1.
Geometric means (loge scale) of observed nodule volumes (symbols) at months 0, 4, 8, and 12 in patients receiving levothyroxine (l-thyroxine), potassium iodide, or no treatment.PPPPPPe

Expected values (obtained by fitting a linear random-effects model to the data) are indicated by lines. Estimated slopes of the linear regression equations with 95% confidence intervals were as follows: patients receiving levothyroxine, −0.04(CI, −0.0567 to −0.0233; < 0.001); patients receiving potassium iodide, −0.02(CI, −0.0361 to −0.0039; = 0.015); patients receiving no treatment, 0.0061 (CI −0.0110 to 0.0232; > 0.2). Comparisons among slopes were as follows: levothyroxine group compared with untreated group, < 0.001; potassium iodide group compared with untreated group, = 0.028; levothyroxine group compared with potassium iodide group, = 0.097. Slopes reported refer to log nodule volume variation for every unit-time (4 months) through the 12-month follow-up.

Grahic Jump Location
Grahic Jump Location
Figure 2.
Geometric means (loge scale) of observed (symbols) and expected (lines) nodule volumes in patients receiving levothyroxine [l-thyroxine], potassium iodide, or no treatment according to the size of nodules.PPPPPPPPP

Estimated slopes of the linear regression equations and 95% confidence intervals were as follows: 1) levothyroxine group: nodule volume of 5 mL or less, −0.049(CI, −0.067 to −0.031; < 0.001); nodule volume of 5 to 10 mL, −0.035(CI, −0.057 to −0.013; < 0.002); nodule volume of 10 mL or greater, −0.023[CI, −0.050 to 0.004; = 0.091]; 2) potassium iodide group: nodule volume of 5 mL or less, −0.026(CI, −0.044 to −0.008; < 0.003); nodule volume of 5 to 10 mL, −0.012(CI, −0.034 to 0.010; = 0.276); nodule volume of 10 mL or greater, −0.0002[CI, −0.028 to 0.027; > 0.2]; 3) untreated group: nodule volume of 5 mL or greater, −0.002(CI −0.020 to 0.016; > 0.2); nodule volume of 5 to 10 mL, 0.013 (CI, −0.012 to 0.038; > 0.2); nodule volume of 10 mL or greater, 0.024 (CI −0.017 to 0.065; > 0.2).

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