Residual Pyramidal Lobe Increases Stimulated Thyroglobulin and Decreases Endogenous Thyroid Stimulating Hormone Stimulation in Differentiated Thyroid Cancer Patients

Objective To determine the frequency of pyramidal lobe remnants after total thyroidectomy (TT) and the effect on stimulated thyroglobulin (Tg). Methods The study included 1740 differentiated thyroid cancer (DTC) patients who were followed up by our center. The department database was searched to identify DTC patients with residual pyramidal lobe after TT. All postoperative technetium-99m pertechnetate thyroid scintigraphy images were re-evaluated for pyramidal lobe residue. Serum stimulated Tg and thyroid stimulating hormone (TSH) levels measured within the first 6 months after TT were retrieved from the database. Results Pyramidal lobe residue was detected in 10.4% of the patients who underwent TT. Evidence of the pyramidal lobe was present on preoperative ultrasonography in 1.6% of the patients with residual pyramidal lobe. Stimulated Tg in patients with pyramidal lobe residue was significantly higher than that in patients without residue (P = .01). Endogenous stimulated TSH in patients with residual pyramidal lobe was significantly lower than that in patients without residue (P = .036). In 5.7% of patients with pyramidal lobe residue, a TSH level of >30 mIU/L was not achieved, which was a significantly higher rate than that in patients without pyramidal lobe residue (P = .034) and is the level required for maximum radioiodine uptake. Conclusion Pyramidal lobe residue was found in almost 10% of DTC patients. The pyramidal lobe is often missed on preoperative ultrasonography. Residual pyramidal lobe increased stimulated Tg and decreased endogenous stimulated TSH. Residual pyramidal lobe may complicate the follow-up of DTC patients.