Transient hypothyroidism associated with increased anti-microsomal antibodies

Risk factors for hypothyroidism in euthyroid thyroid nodule patients with lymphocytic thyroiditis on fine needle aspiration cytology

BACKGROUND/AIMS

Lymphocytic thyroiditis as cytology diagnosis from fine needle aspiration (FNA) is frequently detected in patients with thyroid nodules. However, the clinical outcome for upcoming hypothyroid events has been rarely clarified in euthyroid patients.

METHODS

We retrospectively reviewed the data of patient who had lymphocytic thyroitidis on FNA cytology of thyroid nodule from January 2005 to December 2010 at a tertiary referral hospital. In total, 109 patients with follow-up thyroid function tests (TFT) were enrolled. Final outcomes included overt and subclinical hypothyroidism with thyroid stimulating hormone (TSH) levels ≥ 10 mIU/L. Potential parameters predicting clinical hypothyroidism were analyzed by multivariate analysis.

RESULTS

Over the mean follow-up duration of 51.6 months, 14 out of 109 patients (12.8%) developed clinical hypothyroidism that required thyroid hormone replacement. The median onset time to hypothyroidism was 16 months (range, 3 to 88) and ≥ 60% of patients experienced clinical hypothyroidism within 1 year. By multivariate analysis, background thyroiditis (relative risk [RR], 9.78; p = 0.004), thyroid peroxidase antibody positivity (RR, 9.90; p = 0.003), nodule size (RR, 1.24; p < 0.001), and initial TSH (RR, 1.47; p = 0.009) were the independent risk factors for predicting hypothyroidism in euthyroid patients.

CONCLUSION

Hypothyroidism frequently occurs during the follow-up in euthyroid patients with thyroid nodules which show lymphocytic thyroiditis on FNA cytology. Close surveillance and regular TFT are needed in high-risk patients for upcoming clinical hypothyroidism.

Postpartum autoimmune thyroid syndrome: a model of aggravation of autoimmune disease

Postpartum thyroid dysfunction is rather a common problem during the postpartum period being found in approximately 5% of mothers in the general population. It occurs from subclinical autoimmune thyroiditis that is aggravated after parturition and causes various types of thyroid dysfunction. Immune activity is physiologically suppressed during pregnancy so that the fetus is not rejected, and rebounds above the normal level after parturition. Graves' disease and Hashimoto's thyroiditis also spontaneously ameliorate during pregnancy, and are often aggravated after parturition. The high-risk mothers for postpartum thyroid dysfunction are well screened by antithyroid microsomal antibody (MCAb) and 60% to 70% of MCAb-positive mothers develop postpartum thyroid dysfunction, which is transient in most cases. New onset of Graves' disease may be screened by thyroid-stimulating antibody (TSAb) and 70% of TSAb-positive mothers develop either transient or persistent postpartum Graves' disease that usually occurs 3 to 6 months postpartum. Immune rebound after parturition may cause not only autoimmune thyroid diseases but other autoimmune diseases, which may be investigated with similar strategies to those in postpartum autoimmune thyroid disease. Thus, we found that postpartum onset of rheumatoid arthritis was found in 0.08% of women in the general population and could be partially predicted by measuring rheumatoid factors in early pregnancy. There are several case reports of other autoimmune diseases that develop after delivery; postpartum renal failure or postdelivery hemolytic-uremic syndrome, postpartum idiopathic polymyositis, postpartum syndrome with antiphospholipid antibodies, postpartum autoimmune myocarditis. Many other possible postpartum autoimmune diseases are still unexplored. Puerperal diseases should be carefully examined in relation to autoimmune abnormalities in the affected organs.

Lack of influence of thyroid antibodies on thyroid function in the newborn infant and on a mass screening program for congenital hypothyroidism

Data regarding the incidence and effect of maternal thyroid antibodies on neonatal thyroid function are conflicting. In order to elucidate this aspect, antimicrosomal thyroid antibodies were measured: (1) in cord serum of a normal populations, (2) in the eluate of blood spots of infants with normal filter paper spot T4 and TSH, (3) in the eluate of blood spots from our recalled population (low T4 and normal TSH), and (4) in serum of detected hypothyroid infants. The incidence of MCA with titer greater than 1/40 in cord sera was 8% (115 of 1.383). There was no statistical difference in cord serum T4' T3' or TSH concentrations in these newborn infants compared to the MCA negative population. In 1,000 spots with normal T4 and TSH, 11 or 1.1% were positive for MCA. In 1,630 spots with low T4' 18 positive cases were discovered, or 1.1%. There was excellent correlation between maternal MCA titers and newborn infant titers either in sera or spots when paired samples were available. Finally, only one of 104 detected infants with primary hypothyroidism had detectable MCA. These results indicate a high incidence (8%) of MCA in our presumed normal newborn population, MCA does not decrease serum T4' T3' and TSH concentration or filter paper spot T4 and TSH, and thyroid autoimmunity is not a frequent cause of congenital hypothyroidism.