Why does postpartum thyroiditis cause low milk supply?

Postpartum thyroiditis is inflammation of the thyroid after birth. It can cause a phase of increased thyroid activity followed by reduced thyroid activity, although the pattern differs between people. When thyroid hormone is low, tiredness, feeling cold, constipation, dry skin, slowed thinking and low mood may occur. These changes can affect the energy and hormonal coordination involved in making milk. Feeding frequency, latch, breast drainage, illness, stress and some medicines can also affect supply, so low supply has more than one possible explanation.

Arrange an assessment with a doctor, midwife or lactation professional. Ask for a feeding review and discuss thyroid blood tests if symptoms suggest thyroid dysfunction. Offer feeds as advised, check positioning and attachment, and track wet nappies and your baby's feeding behaviour rather than judging supply by breast fullness alone. Do not start thyroid medicine, herbal products or supplements without professional advice. Tell the clinician that you are breastfeeding so any treatment plan can account for feeding.

Contact a clinician promptly if your baby has fewer wet nappies, seems unusually sleepy, feeds poorly or is not gaining as expected. Seek urgent help for severe weakness, fainting, chest pain, marked breathlessness, confusion or a very fast or irregular heartbeat. These symptoms need assessment rather than being attributed to breastfeeding or normal post-birth tiredness.

Could thyroiditis be affecting my milk supply? Which thyroid tests are appropriate, and when should they be repeated? How can I protect my baby's feeding while supply is assessed? Could another medical issue or medicine be contributing?