Hashimoto's thyroiditis is associated with papillary thyroid carcinoma: role of TSH and of treatment with L-thyroxine.

The possible association between Hashimoto's thyroiditis (HT) and papillary thyroid carcinoma (PTC) is a still debated issue. We analyzed the frequency of PTC, TSH levels and thyroid autoantibodies (TAb) in 13 738 patients (9824 untreated and 3914 under l-thyroxine, l-T(4)). Patients with nodular-HT (n=1593) had high titer of TAb and/or hypothyroidism. Patients with nodular goiter (NG) were subdivided in TAb-NG (n=8812) with undetectable TAb and TAb+NG (n=3395) with positive TAb. Among untreated patients, those with nodular-HT showed higher frequency of PTC (9.4%) compared with both TAb-NG (6.4%; P=0.002) and TAb+NG (6.5%; P=0.009) and presented also higher serum TSH (median 1.30 vs 0.71 µU/ml, P<0.001 and 0.70 µU/ml, P<0.001 respectively). Independently of clinical diagnosis, patients with high titer of TAb showed a higher frequency of PTC (9.3%) compared to patients with low titer (6.8%, P<0.001) or negative TAb (6.3%, P<0.001) and presented also higher serum TSH (median 1.16 vs 0.75 µU/ml, P<0.001 and 0.72 µU/ml, P<0.001 respectively). PTC frequency was strongly related with serum TSH (odds ratio (OR)=1.111), slightly related with anti-thyroglobulin antibodies (OR=1.001), and unrelated with anti-thyroperoxidase antibodies. In the l-T(4)-treated group, when only patients with serum TSH levels below the median value (0.90 µU/ml) were considered, no significant difference in PTC frequency was found between nodular-HT, TAb-NG and TAb+NG. In conclusion, the frequency of PTC is significantly higher in nodular-HT than in NG and is associated with increased levels of serum TSH. Treatment with l-T(4) reduces TSH levels and decreases the occurrence of clinically detectable PTC.

L-thyroxine-treated patients with nodular goiter have lower serum TSH and lower frequency of papillary thyroid cancer: results of a cross-sectional study on 27 914 patients.

The risk of papillary thyroid cancer (PTC) is related to serum TSH, and the development of thyroid autonomy by reducing TSH levels decreases the frequency of PTC in patients with nodular goiter. Our aim was to investigate the effect of L-thyroxine (LT(4)) on the frequency of PTC diagnosed by cytology in a large series of patients with nodular goiter untreated (n=20 055) or treated with L-T(4) (n=7859). L-T(4)-treated patients with respect to untreated patients presented significantly lower serum TSH (median, interquartile range: 0.30 muU/ml, 0.08-0.62 microU/ml versus 0.70 muU/ml, 0.38-1.14 muU/ml; P<0.0001) and prevalence of PTC (3.2 vs 5.1%; P<0.0001). The frequency of PTC was closely related to serum TSH, with it being lowest in patients with TSH below the normal range (<0.4 muU/ml; 189/10 059, 1.9%) and highest in patients with TSH above the normal range (>3.4 muU/ml; 21/127, 16.5%), also showing a progressive increase from the lower to the upper quartile of normal range. A significantly higher proportion of L-T(4)-treated patients (6650/7859, 84.6%) had serum TSH below the median (0.90 muU/ml) with respect to untreated patients (12,599/20,055, 62.8%; chi(2) P value <0.0001), with it being included in the range of TSH associated with a lower frequency of PTC. The relationship between serum TSH and frequency of PTC was unrelated to the type of nodularity (solitary versus multinodular) and was not age dependent. In conclusion, patients with nodular goiter, treatment with L-T(4) is responsible for the reduction of serum TSH and is associated with a decreased frequency of PTC.

Papillary thyroid cancer, although strongly associated with lymphocytic infiltration on histology, is only weakly predicted by serum thyroid auto-antibodies in patients with nodular thyroid diseases.

OBJECTIVE: We evaluated the association between thyroid autoimmunity and thyroid cancer in a retrospective series of unselected thyroid nodules submitted to fine-needle aspiration (FNA) cytology. DESIGN: Anti-thyroid antibodies (TAb) were measured in patients with multinodular goiter (MNG) and single/isolated thyroid nodule (S/I) submitted to FNA. Thyroid lymphocytic infiltration (LI) on histology was studied in a subgroup of patients submitted to thyroidectomy; 13,021 patients were included: on cytology 622 had papillary thyroid cancer (c- PTC) and 12,399 benign thyroid nodular diseases (c-BTN). LI was evaluated in histological samples of 688 patients: 304 with PTC (h-PTC) and 384 with BTN (h-BTN). RESULTS: TAb prevalence was not different in c-BTN and c-PTC (38.7% vs 35.6%). TAb were more frequent in c-BTN than c-PTC in females with MNG (40.1% vs 32.5%, p=0.02), and in c-PTC than in c-BTN in males with S/I (31.2% vs 20.4%, p=0.02) and, although not significantly, in females younger than 30 yr (35.1% vs 30.7%). The frequency and severity of LI was significantly higher in h-PTC than h-BTN, both in MNG (82.5% vs 45.0%, p<0.001) and S/I (85.6% vs 71.0%, p<0.001), but a higher number of patients with h-PTC had negative circulating TAb, despite the presence of moderate/severe LI. CONCLUSIONS: TAb are weakly associated to PTC in males and young females, while they are more frequent in older females with BTN. The frequency and severity of LI is significantly higher in PTC than in BTN, but in cancer patients TAb are frequently negative, despite the evidence of histological thyroiditis. These data suggest that different kinds of immune response may be involved in PTC and BTN.

Lower levels of TSH are associated with a lower risk of papillary thyroid cancer in patients with thyroid nodular disease: thyroid autonomy may play a protective role.

Higher TSH values, even within normal ranges, have been associated with a greater risk of thyroid malignancy. The relationship between TSH and papillary thyroid cancer (PTC) has been analyzed in 10 178 patients submitted to fine needle aspiration of thyroid nodules with a cytology of PTC (n=497) or benign thyroid nodular disease (BTND, n=9681). In 942 patients, submitted to surgery (521 from BTND and 421 from PTC), the histological diagnosis confirmed an elevated specificity (99.6%) and sensitivity (98.1%) of cytology. TSH levels were significantly higher in PTC than in BTND both in the cytological and histological series and also in patients with a clinical diagnosis of multinodular goiter (MNG) and single/isolate nodule (S/I). A significant age-dependent development of thyroid autonomy (TSH <0.4 microU/ml) was observed in patients with benign thyroid disease, but not in those with PTC, diagnosed both on cytology and histology. In patients with MNG, the frequency of thyroid autonomy was higher and the risk of PTC was lower compared to those with S/I. In all patients, the presence of thyroid auto-antibodies (TAb) was associated with a significant increase of TSH. However, both in TAb positive and TAb negative patients TSH levels were significantly higher in PTC than in BTND. Our data confirm a direct relationship between TSH levels and risk of PTC in patients with nodular thyroid diseases. Thyroid autonomy conceivably protects against the risk of PTC, while thyroid autoimmunity does not play a significant role.