The classic description of postpartum thyroiditis includes thyrotoxicosis followed by hypothyroidism. Not all women appear to go through both phases; approximately 1/3 of patients will manifest both, while 1/3 of patients will have only a thyrotoxic or only a hypothyroid phase.
The thyrotoxic phase occurs 1-4 months after delivery of a child and lasts for 1-3 months. It is associated with symptoms including anxiety, insomnia, palpitations (fast heart rate), fatigue, weight loss, and irritability. Since these symptoms may often be attributed to changes after delivery and the stress of having a new baby, the thyrotoxic phase of post-partum thyroiditis is often overlooked.
It is much more common for women to present during the hypothyroid phase. This typically occurs 4-8 months after delivery and may last up to 9 –12 months. Typical symptoms include fatigue, weight gain, constipation, dry skin, depression and poor exercise tolerance. Most women will regain normal thyroid function within 12-18 months after the onset of symptoms. However, approximately 20% of those that go into a hypothyroid phase will remain hypothyroid.