Postpartum Thyroiditis

Postpartum thyroiditis is a condition where there are changes in thyroid function within 12 months of delivery, affecting women without a history of thyroid disease. It can involve thyrotoxicosis (hyperthyroidism), hypothyroidism, or both.

Over time the thyroid function returns to normal, and the patient will become asymptomatic again. A small portion of women will remain hypothyroid and need long-term thyroid hormone replacement.

 

Pathophysiology

The cause of postpartum thyroiditis is not clear. The leading theory is that pregnancy has an immunosuppressant effect on the mother’s body, to prevent her from rejecting the fetus. Once delivery has occurred, there can be an exaggerated rebound effect, with increased immune system activity and expression of antibodies. This may include antibodies that affect the thyroid gland, for example, thyroid peroxidase antibodies. These antibodies cause inflammation of the thyroid gland, leading to over or under activity.

 

Stages

There is a typical pattern of postpartum thyroiditis. Not all women will follow this pattern. There are three stages:

  1. Thyrotoxicosis (usually in the first three months)
  2. Hypothyroid (usually from 3 – 6 months)
  3. Thyroid function gradually returns to normal (usually within one year)

 

Signs and Symptoms

The signs and symptoms of thyrotoxicosis (hyperthyroidism) include:

  • Anxiety and irritability
  • Sweating and heat intolerance
  • Tachycardia
  • Weight loss
  • Fatigue
  • Frequent loose stools

 

The signs and symptoms of hypothyroidism include:

  • Weight gain
  • Fatigue
  • Dry skin
  • Coarse hair and hair loss
  • Low mood
  • Fluid retention (oedema, pleural effusions, ascites)
  • Heavy or irregular periods
  • Constipation

 

Thyroid Function Tests

In thyrotoxicosis, you expect raised T3 and T4 and suppressed TSH. In hypothyroidism, you expect low T3 and T4 and raised TSH.

Thyroid Status

TSH

T3 and T4

Hyperthyroidism

Low

High

Hypothyroidism

High

Low

 

Management

There should be a low threshold for testing thyroid function in women presenting with suggestive symptoms, particularly postnatal depression. Thyroid function tests are performed 6 – 8 weeks after delivery.

Patients with abnormal thyroid function tests in the postpartum period require referral to an endocrinologist for specialist management. Typical treatment is with:

  • Thyrotoxicosis: symptomatic control, such as propranolol (a non-selective beta-blocker)
  • Hypothyroidism: levothyroxine

 

Symptoms and thyroid function tests are monitored, and treatment is altered or stopped as the condition changes and improves.

Women with postpartum thyroiditis require annual monitoring of thyroid function tests, even after the condition has resolved. Monitoring is to identify those that go on to develop long-term hypothyroidism.

 

Last updated September 2020
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