‘Subacute Thyroiditis-Like’Syndromes-Relation to HLA1

Soluble CD4 concentrations predict relapse of post-partum thyroiditis

Post-partum thyroiditis (PPT) is a common autoimmune thyroid disorder which results in significant morbidity at a critical time of a woman's life. The presence of anti-thyroglobulin (anti-TG) and, more so, anti-thryroperoxidase (anti-TPO) antibodies in the first trimester of pregnancy has been reported to forecast subsequent PPT. Despite their predictive value, these tests lack in specificity. We have sought to find an alternative that is more specific and, ideally, which could be tested immediately proximate to the event. We have taken advantage of the high recurrence rate of PPT in subsequent pregnancies to perform a prospective study of serum soluble CD4 (sCD4) and CD8 (sCD8) levels in 22 pregnant women who had at least one previous episode of PPT. This group was matched with 21 pregnant women of comparable age with no evidence of thyroid disease. Both groups of women were sampled in each of the three trimesters of pregnancy, 1 month, 3 months and 6 months post-partum for sCD4, sCD8, thyroid function parameters and antibodies. Twelve of the 22 women with previous PPT had recurrent disease; they were more likely to be cigarette smokers and to have a family history of autoimmune disorders (p<0.05, for both) than those who did not. Half of these women had high anti-TG or anti-TPO each in the first trimester compared to none among those without recurrent PPT and 2/21 controls. Serum sCD8 levels showed no changes over the observation points among the two PPT patient subsets and were comparable to those of the controls. By contrast, serum sCD4 concentrations showed divergent changes in the group with recurrent PPT in the course of pregnancy and postpartum period compared to those without disease recurrence and controls: sCD4 failed to show the physiological fall in the third trimester of pregnancy [19.0+/-1.7 (+/-SD) U/ml vs 15.6+/-2.3 U/ml in controls, NS]. This trend was continued into the first month post-partum when sCD4 levels were clearly higher than in controls (22.1+/-2.6 U/ml compared to 17.9+/-1.9 U/ml in controls, p<0.001) and well before the episode of PPT. An sCD4 serum level outside the 95% reference range at 1 month post-partum (9/12 in recurrent PPT, 1/21 in controls) yields a relative risk of 6.9 (chi2=14.67, p<0.001) compared to 3.3 for first trimester thyroid antibody positivity (p=0.029). In summary, we describe a reliable test for forecasting PPT that can be obtained immediately proximate to the possible event. If our findings are verified in larger studies, the measurement of serum sCD4 concentration drawn in the first month post-partum may prove an ideal test for population screening for impending PPT.

Post-partum hyperthyroidism

The importance of recognizing the frequent occurrence of the destructive (i.e. PPT) and stimulatory (i.e. PGD) causes of PH have been discussed. The estimated prevalence of PH in several geographical regions of Japan, North America and Europe ranges from 2.0-5%. Although the autoimmune basis for GD has been well-established, the clinical and laboratory features of PPT as well as the alterations of humoral and cellular thyroidal immune parameters, the typical needle biopsy evidence of lymphocytic infiltration, and the association with HLA and Gm allotypes associated with the PPT syndrome, favour the view that it is also likely a variant form of subclinical ATD which becomes transiently more active post-partum. Post-partum transient hyperthyroidism with or without transient or permanent hypothyroidism and relapse of GD thyrotoxicosis have been observed in patients with or without a previous history of GD. Hence, an RAIU test is the preferred diagnostic test in differentiating between these two entities, especially in the absence of associated stigmata of GD. When the RAIU test is suppressed, other causes such as thyrotoxicosis factitia and iodine exposure should be excluded. Without an RAIU test, only a rapid and spontaneous resolution of post-partum hyperthyroidism, accompanied by laboratory confirmation of a subsequent hypothyroid phase, can indirectly facilitate the differentiation between PGD and PPT. In the first trimester of pregnancy, an increased FT4I has been proposed as a risk factor for PGD and an increased AMA titre for PPT. Depending upon clinical manifestations, severity, patient and physician preferences, PGD can be treated by one of several choices of conventional therapy. The transient thyrotoxic phase of PPT when relatively asymptomatic may require no therapy, but when symptomatic, only conservative therapy with beta-adrenergic blockers, sedatives and/or tranquilizers is indicated. Close follow-up and long-term surveillance of mothers with PH due to PPT is essential for early detection and management of a possible subsequent hypothyroid phase, which may be symptomatic, but is seldom permanent. Treatment of recurrent episodes of PPT is controversial. Thyrotoxic symptoms are usually mild and transient and can best be managed by symptomatic therapy as indicated. In a few exceptional patients with recurrent episodes, prophylactic treatment with corticosteroid may be warranted but thyroidectomy and ablative radioactive iodine therapy is seldom justified.(ABSTRACT TRUNCATED AT 400 WORDS)

Postpartum autoimmune thyroid disorder associated with HLA-DR4?

Thirteen Danish women with postpartum thyroiditis were HLA-A, B, C and -DR typed. Nine of ten unrelated probands were DR4-positive which is significantly (corrected p = .01) different from the frequency (34.7%) of this antigen in unrelated controls.

Increased frequency of HLA-DR3 and 5 in the syndromes of painless thyroiditis with transient thyrotoxicosis: evidence for an autoimmune aetiology

We studied fifty patients with painless thyroiditis with transient thyrotoxicosis (PTTT) and a low radioiodine thyroidal uptake. In 25 PTTT occurred post-partum (P) and in the remainder was unrelated to pregnancy (U). Seventeen patients with classical subacute thyroiditis were studied for comparison. All patients were typed for HLA-A, B, C, DR antigens. Four of the P patients had recurrences with each pregnancy; two had one previous attack of U; three had a maternal history of Graves' disease; 76% of the P patients had small to moderate goitres and 76% antimicrosomal antibody titres at greater than 1:400. HLA-B35 was found in 24% of P patients compared to 17% of controls; 71% of patients with subacute thyroiditis were, by contrast, B35. Two of P were HLA-B8 positive (versus 25% of controls); 11 patients were HLA-DR3 positive and 15 (60%) HLA-DR5 positive compared to 23% and 27% of controls yielding a relative risk (RR) = 2.50 (P less than 0.05) and 3.83 (P less than 0.005), respectively. All four P patients with recurrences carried HLA-DR5. Thirteen of 25 patients in the U subgroup were HLA-DR3, yielding a RR = 3.38 (P less than 0.01); seven were HLA-DR5, with a non-significant RR = 1.12; four of U had first degree relatives with either autoimmune thyroid disorders or Type 1 diabetes mellitus. Thus, both P and U are associated with HLA-DR3, the P subgroup had in addition an increased frequency of DR5. The observed HLA associations for the PTTT syndromes favours an autoimmune rather than viral aetiology.