Interrelationships between age, thyroid volume, thyroid nodularity, and thyroid function in patients with sporadic nontoxic goiter.

PURPOSE

To test the hypothesis that during the natural history of sporadic nontoxic goiter (SNG), a diffuse goiter precedes a multinodular goiter with gradual development of autonomous thyroid function.

PATIENTS AND METHODS

A cross-sectional survey of 102 consecutive patients with SNG (seven male, 95 female) was performed. Thyroid volume was measured by ultrasonography, and plasma thyroid-stimulating hormone (TSH) by a sensitive assay (TSH immunoradiometric assay).

RESULTS

Patients with a multinodular goiter were older and had a larger thyroid volume than patients with a diffuse or uninodular goiter. Plasma free thyroxine (T4) and total triiodothyronine (T3) were higher and plasma TSH was lower in patients than in normal subjects. Free T4 was higher in the subgroup of patients with a multinodular goiter and a decreased TSH response to thyrotropin-releasing hormone. Plasma TSH (y, in mU/L) was negatively related to thyroid volume (x, in mL): y = 8.2x-0.667 (r = 0.578, p less than 0.001). Thyroid volume (y, in mL) was positively related to age (x, in years): y = -21.8 + 2.0x (r = 0.455, p less than 0.001); and to duration of goiter (x, in years): y = 40.6 + 2.1x (r = 0.505, p less than 0.001). The annual increase in thyroid volume was calculated at 4.5%.

CONCLUSION

The data suggest a continuous growth of SNG and provide support for the concept of increasing thyroid nodularity and autonomy of thyroid function--related to increasing thyroid volume--during the natural history of this disorder.