Post-Partum Thyroiditis

RESUMO DE ABERTURA
  • As an autoimmune disease of the thyroid, Post-partum thyroiditis (PTT) occurs in women within the first postpartum year, characterized by transient episodes of Hyperthyroidism and Hypothyroidism. The classic symptoms of PTT may be mild at the first stage, and easily missed during diagnosis.
  • Symptoms noticed at presentation are similar to the symptoms of Graves’ disease. The level of radioiodine uptake and the presence of thyroid receptor antibodies remains the main differentiating criteria.
  • Serum TSH levels are generally elevated during the Hypothyroidism phase of PTT, however, these are at best indicative of thyroid impairment. The Thyroflex test examines the muscles and skin to measure the speed of reflex conduction as a direct assessment of thyroid functioning. This test trumps the Thyroid Blood Test in accuracy and sensitivity.
  • Surgical intervention is generally not required in cases of Postpartum thyroiditis. In some cases, therapy is not required during the Hyperthyroidism and Hypothyroidism phases as the conditions are self-limiting and resolves with time.

INTRODUÇÃO: Apresentação clínica e visão geral da doença

Post-partum thyroiditis (PTT) is an autoimmune disease of the thyroid characterized by a sequential presentation of transient hyperthyroidism and transient hypothyroidism, or in some cases, hyperthyroidism resolving to permanent hypothyroidism. Generally, this dysfunction occurs within the first postpartum year and has been document to occur, rarely, in cases of miscarriages. The incidence of PTT in postpartum women increases steadily over the years with a global occurrence rate of about 4% – 10% (in women with no history of thyroid disease) and a 70% recurrence rate after the first case in subsequent pregnancies. The probability of developing PPT in women increases significantly with the production of the antithyroid antibody –thyroperoxidase (TPO) –within the first trimester of pregnancy.

Considered the most common endocrinology disorder in postpartum women, PTT is easily confused with Graves’ disease at presentation. However, experts have balanced a distinguishing factor on the presence of thyroid receptor antibodies and levels of radioiodine uptake. Thyroid receptor antibodies are positive in Graves and negative in PTT, while the level of radioiodine uptake is significantly higher in Graves’ when compared with PPT. The disease course is gradual and at the onset can be misdiagnosed as ‘pregnancy anxiety’ or exaggerated biological responses to pregnancy in new mothers. The first phase is characterized by hyperthyroidism with accompanying bout of non-painful thyroid inflammation caused by increased production of thyroid hormones –T4 and/or T3.

The Hyperthyroidism phase presents within the first 6 months after birth and can last for about 2 months. After this period, thyroid hormone levels normalize for a while as the disease progresses to Hypothyroidism. This transient phase occurs within the first 9 months, and lasts for about 6 months. However, it is worthy to note that the clinical course of PPT is not definite for all women and can present in variable forms. The course may include only hyperthyroidism (in 32% of confirmed diagnosis), only hypothyroidism (43%), or a sequential combination of hyperthyroidism and hypothyroidism (25%).

Post-partum thyroiditis and Hashimoto’s shares similar pathogenesis with a few difference in the details. As in Hashimoto’s, diagnosed cases of PPT has shown a close association with lymphocytic infiltration of the thyroid tissue, however, there is little or no evidence of fibrosis or follicular atrophy. Medical enquiries into the causes of PPT has revealed a strong link between the onset of the disease and prior diagnosis of thyroid autoimmunity. As thyroid progresses prior to pregnancy, the titer volumes of anti-thyroid peroxidase antibodies (TPO-Ab) in the blood increases significantly. Severity of inflammation (in some cases) and thyroid destruction is assessed by the level of thyroidal infiltration. Level of infiltration has been closely related to antibody-dependent cell-mediated cytotoxicity and thyroid cell disruption.

Symptom presentation in PPT is based on the disease course. Clinical manifestations of the hyperthyroidism phase are subtle in most cases and include muscle weakness, episodes of anxiety, loss of concentration, palpitations, fatigue, and heat intolerance. Unlike other autoimmune condition of the thyroid, the hypothyroidism phase of PPT is painless and characterized by impaired memory retention rate, dry skin, recurrent fatigue, loss of concentration, weight gain, and constipation.

Abordagem de diagnóstico atual e método de tratamento

Diagnosis of Post-partum thyroiditis is in different care centers around the world is currently balanced on the volume of antithyroid peroxidase antibody (TPOAb) and levels of thyroid stimulating hormone (TSH), and serum free thyroxine (T4). In most diagnosis, there is an elevated level of thyroperoxidase (TPO) antibodies in the first trimester of pregnancy or immediately after childbirth –suggesting ongoing thyroid autoimmunity. TPOAb titer volumes are important diagnostic measures in patients with accompanying cases of Type 1 diabetes or family history of other autoimmune diseases.

Serum TSH levels are generally elevated during the Hypothyroidism phase of PTT. The ranges of upper levels of elevated TSH in the patients varies at different stages of pregnancy, however, a level of 4.0mIU/L is considered the acceptable upper limit in the second and third trimesters. Usually, free thyroxine (T4) levels are decreased in pregnant/postpartum women during the hypothyroidism phase of PTT. Free triiodothyronine levels are considered highly unreliable in women and are mostly excluded in the clinical diagnosis of Post-partum thyroiditis. These parameters are ultimately required to evaluate thyroid functioning during a suspected PTT presentation.

In most healthcare outfits, the diagnostic parameters explained above are usually determined by conducting a Thyroid Blood Test –a popular but highly inaccurate method. Based on the extensive research works and findings of Dr R.I.S Bayliss –a Consultant Endocrinologist with special focus on conditions of the thyroid –only about 18% of the thyroid hormones required to determine thyroid functioning can be found in the blood. About 75% volume of these hormones are found in the skin, muscle and brain. Consequently, Thyroid blood tests are inaccurate in presenting a true picture of thyroid functioning needed for the diagnosis of Post-partum thyroiditis and other common thyroid dysfunctions.

In contrast, the Thyroflex test examines the muscles and skin to measure the speed of reflex conduction as a direct assessment of thyroid functioning. Unlike the controversial blood test, the Thyroflex measures the conduction velocity of reflexes through the tendon and takes into consideration the presenting symptoms and the Resting Metabolic Rate (RMR)

Treatment Protocol for Post-Partum Thyroiditis

Surgical intervention is generally not required in cases of Postpartum thyroiditis. In some cases, therapy is not required during the Hyperthyroidism and Hypothyroidism phases as the conditions are self-limiting and resolves with time. When therapy is required, the choice is based on disease severity, degree of symptoms and the disease course. During the Hypothyroidism phase, women showing symptoms can be treated with levothyroxine (T4). Clinical trials have reported improved outcomes in hypothyroid women with positive TPO antibodies. Levothyroxine is also used in the treatment of hypothyroid women with no TPO antibodies but a raised level of TSH.

This therapy method is aimed at normalizing the different levels of raised TSH during pregnancy and also improve thyroid functioning as the disease resolves. Women placed on Levothyroxine are closely monitored and dose increments are implemented if necessary. Treatment can be continued for 12 months and stopped only when thyroid functioning has evidently improved.

In the management of Post-partum thyroiditis, it is important that patients at risk of permanent hypothyroidism be identified and placed on an appropriated therapy plan. Patients are generally advised to separate Levothyroxine doses from calcium or iron-containing medications to avoid a decrease in the level of Levothyroxine absorption. The Thyroflex Test has been proven to improve the prognosis of PTT as accurate diagnosis is made on time when compared with the Thyroid Blood Test.

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