Serum thyroglobulin levels after fine-needle aspiration of thyroid nodules

To investigate whether a minor insult to the thyroid gland attributable to fine-needle aspiration (FNA) or external thyroid palpation can cause a release of serum thyroglobulin (Tg) into the circulation.

We determined serum Tg levels before and at 60 minutes and 15 days after FNA in 25 patients with thyroid nodules. Results were compared with those obtained in 25 patients with thyroid nodules, in whom serum Tg concentrations were determined before and 60 minutes after palpation of the thyroid, and in 15 healthy subjects without thyroid disease, who had no thyroid palpation and no FNA, from whom 2 blood specimens were obtained 60 minutes apart. All participants had normal results of thyroid function tests and no detectable antithyroglobulin or thyroid peroxidase antibodies.

After FNA, 22 of 25 patients had significant elevation of serum Tg concentrations. The Tg levels returned to baseline values 15 days after FNA. In 4 of the 25 patients with thyroid nodules who had palpation of the thyroid, a significant increase in serum Tg levels was elicited. None of the 15 healthy subjects with normal thyroid glands (and with no FNA or thyroid palpation) had significant Tg elevations.

FNA causes a significant increase in serum Tg concentrations, which may persist for 15 days. Therefore, Tg assay should not be scheduled prematurely after FNA.