RESUMO
BACKGROUND: Twenty-twenty-five percent of patients with differentiated thyroid cancer (DTC) can have elevated thyroglobulin antibodies (TgAb). The study aimed to find any prognostic significance of elevated TgAb during follow-up. METHODS: Ten-year retrospective study from a tertiary center including 79 patients with raised TgAb after total/staged thyroidectomy for DTC. We identified patients with stable (7.6%), increasing (15%) and decreasing levels of TgAb (77.2%); groups 1, 2 and 3 respectively. During follow-up we analyzed TgAb in subcategories by TgAb trend (>50% rise, <50% rise, >50% decline, <50% decline, positive to negative/normalization, negative to positive and stable levels), gender, age, surgery, autoimmune disease, histology, RAI uptake, distant metastases, and recurrence. RESULTS: The incidence of raised TgAb levels was 33.2%, with female predominance. No connection was identified regarding other parameters. 11.4% had distant metastases. The highest mean maximum levels of TgAb was in group 2 (1918.75 IU/mL) and the lowest in group 3 (412.70 IU/mL). The recurrence rate changed significantly between the 3 groups: 50% in group 1, 75% in group 2, and 25% in group 3 (P=0.002). Recurrence rates decreased to 15% in the subcategory where TgAb became negative/normal from positive (P=0.0001). In patients with a negative to positive TgAb level trend or >50% rise, recurrence rates were 100% (P=0.041) and 70% (P=0.012) respectively. CONCLUSIONS: Patients with increasing TgAb levels during follow-up have a higher rate of recurrence, distinctly for those with negative to positive trend and >50% rise in TgAb. These patients need closer follow-up, and TgAb may be used as a dynamic follow-up marker.
RESUMO
A 47-year-old man was commenced on levothyroxine following a diagnosis of subclinical hypothyroidism with nonspecific symptoms. Despite increasing doses of levothyroxine, his thyroid-stimulating hormone (TSH) remained elevated and he was referred for further assessment as he was unable to tolerate further titration. On assessment, his thyroid function demonstrated an elevated TSH and elevated free-T4. The initial impression was of iatrogenic thyrotoxicosis, with possible underlying thyroid hormone resistance, TSHoma or assay interference. After discontinuation of levothyroxine, free-T4 normalised but TSH remained elevated. There was a normal response to thyrotropin-releasing hormone (TRH) testing. T3 suppression testing demonstrated free-T4 reduction but persistently high TSH. THRß sequencing was normal. TSH measurement by alternative assays revealed discrepant results. Gel filtration chromatography revealed the presence of high-molecular weight TSH variant alongside normal TSH. Macro-TSH is a rare phenomenon with spuriously elevated TSH and which may mimic subclinical hypothyroidism. Recognition of macro-TSH avoids misdiagnosis and prevents inappropriate treatment.
