The thyroid is a gland found in the front of your neck. It secretes hormones that play an important part in lactation by regulating prolactin and oxytocin.

Thyroid disorders impact a woman’s health in a variety of ways. When the thyroid is not functioning correctly, it can impact milk production. There is also connection between thyroid disorders and autoimmune problems. The immune system is suppressed during pregnancy to protect your baby. This is a good thing. You don’t want your body reacting to your growing baby as a foreign invader!  Problems with the thyroid can begin before or during pregnancy, in the postpartum period, or later in life. They can also occur along with other medical conditions, which can make diagnosis and treatment more challenging.

Thyroid disease is diagnosed through blood tests that measure the levels of thyroid stimulating hormone (TSH) triisdothyrine (T3)/tetra-iodothyronine (thyroxine or T4). It is also recommended that iodine levels be monitored and treated, if they are not at appropriate levels. Let your obstetrician and personal care physician know if there is a family history of thyroidism.

The most common forms of thyroidism are hyperthyroidism, hypothyroidism, and postpartum thyroid dysfunction.

Hypothyroidism (underactive thyroid)
  • Indicated when the TSH level is high and T3/T4 levels are low.
  • Symptoms – dry skin, sensitivity to cold, “baby blues” and/or depression, fatigue, hair loss, lack of energy, forgetfulness, constipation, increased menstrual frequency and flow, mild enlargement of the thyroid.
  • Most common form is Hashimoto’s disease.
  • Thyroid hormone replacement is a common form of treatment especially during pregnancy and breastfeeding.
  • In pregnancy, this can result in pregnancy-induced hypertension and low birth weight.
  • Mothers with hypothyroidism are at risk for delayed or insufficient milk production.
  • Studies also indicate there may be a negative effect on oxytocin.
Hyperthyroidism  (overactive thyroid)
  • Indicated when the TSH level is low and the T3/T4 levels are high.
  • Symptoms – racing heart, feeling nervous/anxious, sweating, tremors, muscle cramps, fatigue, tired, run down, weight loss, sensitivity to heat, diarrhea, decreased menstrual frequency and flow, mild enlargement of the thyroid.
  • Most common form is Grave’s disease.
  • Pregnancy can induce a mild form due to the increased rates of clearance of T3/T4 levels in the blood plasma. Some mothers with hyperthyroidism may notice an easing of symptoms in the second and third trimesters, but symptoms can rebound after delivery.
  • Those with hyperthyroidism are at risk for premature delivery, pre-eclampsia, fetal growth restriction and increased mortality for mother and baby.
  • Studies also indicate there may be negative impact on prolactin and oxytocin concentrations.
  • Treatments:
    • Studies have indicated that propylthiouracil (PTU) is the drug of choice for a breastfeeding mother in this instance. It is excreted in small amounts into breastmilk and does not impact baby’s thyroid function.
    • Methimazole is an accepted option, baby should be monitored frequently.
Postpartum thyroid dysfunction
  • Four types:
    • Postpartum thyroid dysfunction (PPT)
    • Postpartum Grave’s disease
    • Postpartum pituitary infarction (Sheehan’s syndrome) – often associated with excessive blood loss during/after delivery
    • Lymphocytic hypophysitis
  • Occurs in about 5-7% of all pregnancies.
  • Women with diabetes mellitus type 1 are at three times the risk.
  • Women who smoke are at three times the risk.
  • Symptoms – intolerance to cold, dry skin, lack of energy, impaired concentration, aches and pains.
  • Typically starts with aspects of hyperthyroidism that can last up to several weeks and the transition to hypothyroidism, which can last for several months. This state is more obvious clinically, leading to treatment.
Impact on Breastfeeding

Thyroid issues often cause difficulty with milk supply and with milk removal. Mothers may find their thyroid levels change with pregnancy and childbirth, which is why frequent testing of mother is recommended. Depending on the medication, your baby’s levels may also need to be checked regularly postpartum.

Suggested management to support breastfeeding
  • Regular follow-up with physician, regular screening for hypothyroidism in first year.
  • Important to work on improving milk removal.
  • Pitocine/oxytocin nasal spray – may provide the extra hormone needed to eject milk.
  • Massaging breast – massage from outer reaches of the breast toward the nipple may make more milk available.
  • Breast compressions during feedings – mechanically increasing internal pressures may help propel milk from the breast.
  • Galactagogues – effective only if milk can be removed and thyroid levels are in balance, then can be useful as supportive treatment.
  • Delay any radioactive tests or treatments until no longer breastfeeding if at all possible. If a scan using a radioactive material must be done, request the use of a radioactive material with the shortest half-life, which will result in the shortest interruption of breastfeeding.
  • It is possible to resume breastfeeding immediately after a scan using contrast dye as the dye is not absorbed.
Breastfeeding Reminders
  • Observe the cues of effective feeding:
    • Adequate output.
    • Hearing swallows.
    • Breasts fuller before feeding and softening with feeding.
  • Observe baby’s weight gain – that it remains consistent throughout the first year.
  • Continue with any thyroid medications as prescribed.
  • Check thyroid levels frequently to maintain levels at the upper part of the normal range.
  • Communicate your treatment to all physicians involved in your care and encourage them to coordinate care together.

American College of Radiology. Manual on Contrast Media, p.102-103., accessed Mar 15, 2018


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