Thyroid Conditions and Breastfeeding
Thyroid conditions are relatively common, including during pregnancy and the postnatal period. Thyroid hormones have an important role in the body, including metabolism, energy regulation, pregnancy and lactation.
Most people with a thyroid condition can breastfeed. A diagnosis does not automatically mean that breastfeeding will be difficult or that breastmilk production will be affected. However, some thyroid conditions can influence maternal health, milk production or, in particular circumstances, a baby's thyroid function after birth.
Understanding the differences between thyroid conditions, recognising when further assessment may be needed and knowing how treatment fits alongside breastfeeding can help families access appropriate support.
Thyroid function and breastfeeding
The thyroid gland produces hormones that help regulate metabolism and influence the function of many body systems. Thyroid hormones also have a role in reproductive health, pregnancy and the physiological changes involved in establishing lactation.
During pregnancy, thyroid hormone requirements change. After birth, the body undergoes further hormonal adjustments as lactation becomes established. A thyroid condition that is untreated, inadequately controlled or develops during the postnatal period may therefore be relevant to maternal wellbeing and breastfeeding.
The effect varies according to the underlying condition, its severity and whether thyroid hormone levels are adequately managed.
Common thyroid conditions
Hypothyroidism and Hashimoto’s thyroiditis
Hypothyroidism occurs when the thyroid gland does not produce enough thyroid hormone. Hashimoto’s thyroiditis is an autoimmune condition and a common cause of hypothyroidism.
Symptoms can include fatigue, feeling cold, constipation, dry skin, difficulty concentrating and low mood. Some symptoms overlap with the physical and emotional changes associated with pregnancy and caring for a newborn, which can make a thyroid condition harder to recognise.
Untreated or inadequately treated hypothyroidism may affect general health and has been associated with difficulties establishing or maintaining milk production. Appropriate treatment and monitoring are important, including after birth when thyroid hormone requirements may change.
Graves’ disease and hyperthyroidism
Hyperthyroidism occurs when the thyroid gland produces excessive thyroid hormone. Graves’ disease is an autoimmune condition and an important cause of hyperthyroidism.
Symptoms may include palpitations, a racing heartbeat, anxiety, tremor, heat intolerance, sweating, weight loss and difficulty sleeping. These symptoms can be distressing and may overlap with experiences during the postnatal period.
Graves’ disease is particularly relevant to newborn health because thyroid-stimulating receptor antibodies (TRAb) can cross the placenta and affect the baby's thyroid gland. This can happen even if the birthing parent has previously received treatment for Graves’ disease, including thyroid surgery or radioactive iodine, and no longer has an overactive thyroid.
Postpartum thyroiditis
Postpartum thyroiditis is an inflammation of the thyroid gland that develops during the first year after birth. It is thought to be an autoimmune process and can occur in people who have no previous diagnosis of thyroid disease.
It may involve an initial phase of excessive thyroid hormone release, followed by a period of reduced thyroid hormone production. Not everyone experiences both phases, and some people develop only one.
Postpartum thyroiditis is particularly important because its symptoms can be mistaken for the physical and emotional demands of caring for a newborn.
Symptoms may include anxiety, irritability, palpitations, fatigue, low mood, difficulty concentrating and changes in weight. The hypothyroid phase can also contribute to low energy and feeling overwhelmed.
Changes in mood, anxiety or emotional wellbeing should not automatically be attributed to thyroid dysfunction. Equally, these experiences should not be dismissed as simply part of new parenthood. Anyone struggling with their mental health should be encouraged to seek support from their GP, midwife or health visitor. Thyroid function testing may be appropriate where symptoms suggest a possible thyroid problem.
Breastfeeding aversion can also occur for a range of reasons and may be particularly difficult to manage alongside postnatal exhaustion or changes in wellbeing. Breastfeeding aversion: help and what can make it easier.
Understanding the differences
| Condition | What happens | Potential relevance after birth | |---|---|---| | Postpartum thyroiditis | Inflammation causes stored thyroid hormone to be released, sometimes followed by reduced hormone production. | Can affect maternal wellbeing and may require monitoring or treatment. | | Graves’ disease | Autoantibodies stimulate the thyroid gland to produce excessive thyroid hormone. | Maternal antibodies can cross the placenta and cause neonatal thyroid dysfunction. | | Thyroid storm (thyrotoxic crisis) | A rare, life-threatening deterioration associated with severe thyrotoxicosis. | A medical emergency requiring urgent hospital treatment. |
Adapted from Korevaar et al. (2026), RCOG (2025) and Taylor et al. (2026).
Thyroid storm: a medical emergency
Thyroid storm, also known as thyrotoxic crisis, is a rare but life-threatening complication of severe hyperthyroidism. It involves an acute deterioration in several body systems and requires emergency hospital treatment.
Symptoms may include a very high temperature, marked tachycardia, agitation or confusion, vomiting, diarrhoea, dehydration and cardiovascular complications. It is not simply an episode of anxiety, palpitations or feeling unwell.
Although rare, thyroid storm is a medical emergency. Anyone experiencing symptoms suggestive of severe thyrotoxicosis with significant deterioration should seek emergency medical attention (Taylor et al., 2026).
Medication and breastfeeding
Thyroid conditions may require prescribed medication to regulate thyroid hormone levels or manage symptoms. The choice of treatment will depend on the specific condition, its severity and individual circumstances. Your GP or endocrinologist will advise on appropriate treatment, including whether any changes are needed following pregnancy.
Medication doses are guided by thyroid function blood results and clinical assessment. Requirements can change over time, particularly during pregnancy and after birth. Do not adjust, reduce or increase your dose, or stop taking prescribed medication, without first discussing this with your healthcare professional.
Many medicines used to manage thyroid conditions are compatible with breastfeeding. However, this depends on the medication and treatment being prescribed, so discuss any concerns with your healthcare professional rather than stopping or changing medication yourself. If you are breastfeeding, chestfeeding or expressing milk, make sure your prescriber knows so that this can be considered when treatment is selected.
Non-pharmaceutical remedies, including herbal preparations and supplements marketed for thyroid support, are not a substitute for medical assessment and prescribed treatment. There is insufficient evidence that these products can effectively treat thyroid dysfunction, and some may interfere with thyroid function or prescribed medication. Supplements containing iodine or kelp require particular caution because excessive iodine intake can adversely affect thyroid function. Discuss any supplements or complementary treatments with your healthcare professional before starting them (NICE, 2019, updated 2023; NHS, 2025).
Thyroid function and milk production
Thyroid hormones play an important role in normal mammary gland development and lactation. They interact with other hormones involved in milk production and influence the metabolic processes required to establish and maintain lactation. Adequate thyroid hormone levels are therefore part of the physiological conditions needed for normal lactation.
Research has identified an association between hypothyroidism and difficulties with milk production, and some reports describe improvement following appropriate thyroid hormone replacement. However, much of the available human evidence is limited, and the relationship between thyroid dysfunction, milk production and breastfeeding duration is not yet fully understood. The 2026 American Thyroid Association guideline acknowledges this uncertainty and concludes that clinically significant effects are unlikely in most cases (Alexander et al., 2017; Korevaar et al., 2026).
The evidence relating to excessive thyroid hormone levels and milk production is also limited. It is therefore important not to assume that all thyroid conditions have the same effect on lactation.
Thyroid function should be considered when investigating unexplained low milk production or difficulties establishing lactation, alongside other potential physiological and feeding-related factors. A thyroid condition should not automatically be assumed to be the cause, but neither should its potential contribution be overlooked.
An International Board Certified Lactation Consultant (IBCLC) can help assess the feeding dyad, including milk transfer, feeding effectiveness, milk production and the practicalities of breastfeeding or expressing. This assessment can help identify feeding-related factors and establish whether further medical investigation may be appropriate. An IBCLC does not replace medical assessment or treatment of thyroid conditions.
For further information, see What is an IBCLC? Feeding support explained, Breastfeeding latch and positioning and How to express breastmilk.
Thyroid testing after birth
People with a known thyroid condition may need further blood tests after birth to check thyroid hormone levels and review whether their treatment remains appropriate. Thyroid hormone requirements can change during pregnancy and after delivery, so medication doses may need to be reviewed. The timing and frequency of testing depend on the underlying condition, treatment and individual circumstances. Your GP or endocrinology team can advise on the monitoring needed (NICE, 2019, updated 2023; RCOG, 2025).
For example, RCOG advises that thyroid blood tests should be checked around six weeks after birth to review treatment. People with Graves’ disease or other forms of hyperthyroidism may also need postnatal monitoring. The appropriate plan will depend on their individual circumstances.
Postpartum thyroiditis can also develop in people without a previous thyroid diagnosis. Symptoms may initially be attributed to tiredness, anxiety or the demands of caring for a newborn. Where symptoms are persistent, unexplained or concerning, a GP can assess whether thyroid function testing is appropriate.
The 2026 American Thyroid Association guideline recognises that the relationship between thyroid function and lactation difficulties is not fully established. There is insufficient evidence to recommend routine thyroid screening or treatment solely to improve milk production. This does not mean that thyroid function should be overlooked where there are other symptoms, a known thyroid condition or clinical reasons to investigate it (Korevaar et al., 2026).
When a baby needs additional thyroid monitoring
Most babies born to people with thyroid conditions do not develop thyroid problems. However, certain maternal conditions, antibodies and treatments during pregnancy can place a baby at increased risk.
This is particularly important where the birthing parent:
Has current or previous Graves’ disease, including where the thyroid gland has been surgically removed or treated with radioactive iodine.
Has raised thyroid-stimulating receptor antibodies (TRAb).
Has taken antithyroid medication, such as carbimazole or propylthiouracil (PTU), during pregnancy.
TRAb antibodies can cross the placenta and stimulate the baby's thyroid gland. Antithyroid medication can also cross the placenta and temporarily suppress the baby's thyroid function. These effects can occur together, meaning that a baby may initially appear well before developing signs of thyroid dysfunction.
A baby's risk depends on the maternal history, antibody levels and treatment during pregnancy. The neonatal or paediatric team should be informed of relevant thyroid history so that appropriate assessment and monitoring can be arranged.
Where indicated, thyroid blood tests may be taken shortly after birth and repeated at around one to two weeks of age. The timing and need for further testing will be determined by the baby's clinical team (RCOG, 2025; van der Kaay et al., 2016).
Not every maternal thyroid condition requires additional neonatal testing. For example, uncomplicated hypothyroidism without relevant antibodies or antithyroid medication exposure does not automatically mean that a baby needs extra thyroid monitoring.
Signs of thyroid problems in newborn babies
Neonatal hyperthyroidism can cause symptoms that may not be obvious immediately after birth. Symptoms can develop over the first few weeks as the effects of maternal antithyroid medication reduce while stimulating antibodies remain active.
Possible signs include:
Difficulty feeding or poor weight gain despite an increased appetite.
Irritability, restlessness, jitteriness or difficulty sleeping.
A persistently fast heartbeat or abnormal heart rhythm.
Excessive sweating, flushing or heat intolerance.
Vomiting or diarrhoea.
Breathing difficulties.
An enlarged thyroid gland (goitre).
Prominent or staring eyes.
Jaundice or other signs of systemic illness.
Not all babies will show the same symptoms, and some may have no obvious signs initially. A baby with a relevant maternal history should receive the recommended monitoring even if they appear well.
Any concerns about a newborn's feeding, behaviour, breathing, heart rate or general condition should be discussed promptly with a healthcare professional. Severe breathing difficulties, marked lethargy or significant deterioration require emergency assessment (Endotext, 2019; van der Kaay et al., 2016).
Congenital hypothyroidism and newborn screening
Congenital hypothyroidism is a condition in which a baby is born with insufficient thyroid hormone production. Thyroid hormones are essential for normal growth and brain development, so early identification and treatment are important.
In the UK, congenital hypothyroidism is included in the NHS newborn blood spot screening programme. The heel-prick test is usually offered when a baby is around five days old. The screening laboratory measures thyroid-stimulating hormone (TSH) in the blood spot sample to help identify babies who may have congenital hypothyroidism. Where a screening result suggests possible congenital hypothyroidism, further testing and treatment are arranged (NHS, 2025; NHS England, 2024).
Routine newborn screening does not replace additional thyroid testing where a baby is considered at risk because of maternal Graves’ disease, raised TRAb antibodies or antithyroid medication exposure during pregnancy. These are separate clinical considerations and may require a different monitoring pathway.
Considerations for infant procedures
A known or suspected thyroid condition in a baby is relevant to decisions about elective procedures, including frenulotomy.
Thyroid dysfunction can affect heart rate, metabolism and general physiological stability. Where a baby has suspected or confirmed neonatal thyroid dysfunction, the priority is paediatric assessment and medical management before an elective procedure is considered.
An infant with suspected or confirmed neonatal thyroid dysfunction should not undergo elective tongue-tie release in a non-hospital setting; paediatric assessment and medical stabilisation are required before any decision about the procedure and its appropriate setting is made.
The appropriate timing and setting for any procedure should be determined following assessment by the relevant medical team, taking account of the baby's clinical condition and any associated risks (RCoA, 2025).
Joined-up care
Thyroid conditions do not automatically prevent breastfeeding. Many people with thyroid disorders breastfeed successfully with appropriate assessment, treatment and support.
When feeding difficulties or low milk production occur, it is important to consider the whole feeding picture rather than assuming that thyroid dysfunction is the cause. Milk production, milk transfer and the effectiveness of feeding are related, but they are not the same thing.
Where milk production is lower than expected, assessment may need to consider thyroid function alongside other maternal health factors, milk removal, feeding frequency and the effectiveness of milk transfer. My article Protecting breast milk supply when feeding is inefficient explains why ineffective milk removal can affect ongoing production and why protecting supply may need to be considered while feeding difficulties are being investigated.
Families should not have to work through persistent feeding difficulties alone. An appropriately qualified infant-feeding professional can help assess the feeding dyad, including positioning, attachment, sucking, swallowing, milk transfer, feeding effectiveness and milk production. This can help identify where practical feeding support may be useful and whether further medical assessment or referral is needed.
An International Board Certified Lactation Consultant (IBCLC) has specialist knowledge of lactation and breastfeeding and can support families with concerns about milk production, milk transfer, feeding difficulties and expressing. Other infant-feeding professionals, including midwives, health visitors and specialist feeding teams, may also have an important role depending on the family's needs.
You can read more about what an infant-feeding specialist does, what an IBCLC is and how they support infant feeding, and when a lactation consultant can support you.
Medical assessment remains important where thyroid dysfunction is suspected or a known condition needs monitoring. An IBCLC or other feeding specialist does not replace GP or endocrinology care, but can help ensure that feeding needs are recognised and supported alongside medical treatment.
Joined-up care means considering both the health of the person breastfeeding and the needs of the baby, without overlooking either the possible medical contributors or the practical support that can make feeding more manageable.
References
Alexander, E.K. et al. (2017) ‘2017 Guidelines of the American Thyroid Association for the Diagnosis and Management of Thyroid Disease During Pregnancy and the Postpartum’, Thyroid, 27(3), pp. 315–389. doi: 10.1089/thy.2016.0457.
Chan, S. et al. (2025) ‘Management of thyroid disorders in pregnancy’, BJOG, 132(8), pp. e130–e161. doi: 10.1111/1471-0528.18088.
Drugs and Lactation Database (LactMed®) (2026) ‘Levothyroxine’. Last revised 15 October 2026. National Library of Medicine. Available at: https://www.ncbi.nlm.nih.gov/books/NBK501003/.
Endotext (2019) ‘Neonatal hyperthyroidism’. Available at: https://www.ncbi.nlm.nih.gov/books/.
Korevaar, T.I.M. et al. (2026) ‘American Thyroid Association 2026 Guidelines for Thyroid Disease in Preconception, Pregnancy, and Postpartum’, Thyroid, 36(5), pp. 481–544. doi: 10.1177/10507256261445624.
National Institute for Health and Care Excellence (NICE) (2019, updated 2023) Thyroid disease: assessment and management. NICE guideline NG145. Available at: https://www.nice.org.uk/guidance/ng145.
NHS (2025) ‘Iodine’. Vitamins and minerals. Available at: https://www.nhs.uk/conditions/vitamins-and-minerals/iodine/.
NHS (2025) ‘Newborn blood spot test’. Available at: https://www.nhs.uk/baby/newborn-screening/blood-spot-test/.
NHS England (2024) Laboratory guide to screening for congenital hypothyroidism in the UK. Available at: https://www.gov.uk/government/publications/congenital-hypothyroidism-screening-laboratory-handbook.
NHS Specialist Pharmacy Service (2023) ‘Using beta-blockers during breastfeeding’.
Royal College of Anaesthetists (RCoA) (2025) Guidelines for the Provision of Paediatric Anaesthesia Services.
Royal College of Obstetricians and Gynaecologists (RCOG) (2025) ‘Thyroid problems in pregnancy’. Available at: https://www.rcog.org.uk/for-the-public/browse-our-patient-information/thyroid-problems-in-pregnancy/.
Taylor, P.N. et al. (2026) ‘Management of thyroid emergencies: joint consensus statement on management of thyroid storm’, European Thyroid Journal, 15(4), ETJ260043. doi: 10.1530/ETJ-26-0043.
van der Kaay, D.C.M. et al. (2016) ‘Management of neonates born to mothers with Graves’ disease’, Pediatrics, 137(4), e20151878.
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