maternal hypothyroidism

Question 1

Describe overt maternal hypothyroidism.

Answer 1

Overt maternal hypothyroidism is defined as TSH >10mIU/L with FT4 of any level OR TSH >4mIU/L with FT4 below lower limit of trimester-specific reference range. It occurs in 1-2% of pregnancies and can be caused by Hashimoto’s thyroiditis, previous radioiodine therapy, previous thyroidectomy, previous post-partum thyroiditis, or hypopituitarism. It can lead to maternal complications such as miscarriage and pre-eclampsia, and fetal complications such as premature delivery, low birthweight, and impaired neurological development.

Question 2

What are the common causes of overt maternal hypothyroidism?

Answer 2

The common causes of overt maternal hypothyroidism are Hashimoto’s thyroiditis, previous radioiodine therapy, previous thyroidectomy, previous post-partum thyroiditis, and hypopituitarism.

Question 3

What are the maternal complications of overt maternal hypothyroidism?

Answer 3

The maternal complications of overt maternal hypothyroidism include miscarriage and pre-eclampsia.

Question 4

What are the fetal complications of overt maternal hypothyroidism?

Answer 4

The fetal complications of overt maternal hypothyroidism include premature delivery, low birthweight, and impaired neurological development.

Question 5

What is the prevalence of overt maternal hypothyroidism in pregnancies?

Answer 5

Overt maternal hypothyroidism occurs in 1-2% of pregnancies.

Question 6

What is the recommended TSH level for women on levothyroxine during preconception counseling?

Answer 6

In women on levothyroxine, the aim is to keep TSH in the lower half of the non-pregnant reference range during preconception counseling.

Question 7

What should be done once pregnancy is confirmed in women on levothyroxine?

Answer 7

Once pregnancy is confirmed, TFTs should be urgently checked. If not possible, the levothyroxine dose should be increased by 30% to ensure optimal early neurological development, and TFTs should be checked as soon as possible.

Question 8

What is the recommended TSH level during pregnancy for women on levothyroxine?

Answer 8

During pregnancy, women on levothyroxine should aim for TSH within the local normal trimester-specific range.

Question 9

What is the recommended treatment for overt maternal hypothyroidism?

Answer 9

The recommended treatment for overt maternal hypothyroidism is levothyroxine. Armour thyroid and liothyronine are not recommended.

Question 10

What should be done post-partum for women with overt maternal hypothyroidism?

Answer 10

Post-partum, women with overt maternal hypothyroidism should return to their pre-pregnancy doses of thyroxine and have their thyroid function checked in 4 weeks.

Question 11

Describe subclinical maternal hypothyroidism.

Answer 11

Subclinical maternal hypothyroidism is defined as TSH > upper limit of trimester-specific reference range, but <10IU/L, with FT4 in the normal range. It may increase the risk of miscarriage, preterm birth, hypertension, and eclampsia. There is inconsistent evidence for its effect on fetal birthweight, and no evidence that it affects fetal cognitive development.

Question 12

What are the maternal complications of subclinical maternal hypothyroidism?

Answer 12

The maternal complications of subclinical maternal hypothyroidism may include an increased risk of miscarriage, preterm birth, hypertension, and eclampsia.

Question 13

What are the fetal complications of subclinical maternal hypothyroidism?

Answer 13

The fetal complications of subclinical maternal hypothyroidism are inconsistent, with evidence showing no effect on fetal cognitive development and inconsistent evidence for its effect on fetal birthweight.

Question 14

What is the recommended treatment for subclinical maternal hypothyroidism?

Answer 14

There is no evidence that treatment with levothyroxine improves outcomes for subclinical maternal hypothyroidism. However, treatment is recommended if TSH >4 or above the trimester-specific normal range, regardless of FT4.

Question 15

What is the natural history of subclinical maternal hypothyroidism?

Answer 15

2-5% per year progress to frank hypothyroidism.

Question 16

Describe isolated hypothyroxinaemia.

Answer 16

Isolated hypothyroxinaemia is defined as TSH within the trimester-specific reference range, but FT4 below the lower limit for that trimester. Risk factors include iodine deficiency, excess, and raised BMI. It does not have any known maternal complications, but mild impairment in neurocognitive tests has been demonstrated in childhood.

Question 17

What are the risk factors for isolated hypothyroxinaemia?

Answer 17

The risk factors for isolated hypothyroxinaemia include iodine deficiency, iodine excess, and raised BMI.

Question 18

What are the fetal complications of isolated hypothyroxinaemia?

Answer 18

The fetal complications of isolated hypothyroxinaemia include mild impairment in neurocognitive tests demonstrated in childhood.

Question 19

What is the recommended treatment for isolated hypothyroxinaemia?

Answer 19

There is no evidence that treatment with levothyroxine improves outcomes for isolated hypothyroxinaemia, so treatment is not recommended.

Question 20

What are the maternal risks of being euthyroid but TPO antibody positive?

Answer 20

The maternal risks of being euthyroid but TPO antibody positive include an increased risk of miscarriage, developing overt hypothyroidism, and post-partum thyroiditis.

Question 21

What are the fetal complications of being euthyroid but TPO antibody positive?

Answer 21

The fetal complications of being euthyroid but TPO antibody positive include a risk of preterm birth.

Question 22

What is the recommended treatment for being euthyroid but TPO antibody positive?

Answer 22

There is no robust evidence that treatment with levothyroxine improves pregnancy rates or outcomes for women who are TPO antibody positive and euthyroid. However, low-dose levothyroxine can be considered in women with recurrent pregnancy loss.

Question 23

What should be done in terms of thyroid function testing for women with TPO antibodies during pregnancy and post-partum?

Answer 23

TFTs should be checked in the 3rd trimester and 3 months post-partum to look for evolving thyroid disease. Up to 20% of women with TPO antibodies develop frank hypothyroidism by the 3rd trimester.

Question 24

What is the prevalence of post-partum thyroid dysfunction?

Answer 24

Post-partum thyroid dysfunction occurs in 5-10% of women within 1 year of delivery or miscarriage. It is 3 times more common in women with T1DM and more common in women who are TPO antibody positive.

Question 25

What is the etiology of post-partum thyroid dysfunction?

Answer 25

The etiology of post-partum thyroid dysfunction is chronic autoimmune thyroiditis.

Question 26

What are the clinical presentations of post-partum thyroid dysfunction?

Answer 26

Post-partum thyroid dysfunction can present as hyperthyroidism (32%), hypothyroidism (43%), or hyperthyroidism followed by hypothyroidism (25%). Hyperthyroidism typically develops within 4 months of delivery and presents as fatigue. Hypothyroidism develops 4-6 months after delivery and may be mild and non-specific. Hyperthyroidism followed by hypothyroidism usually resolves spontaneously within 6-12 months of delivery.

Question 27

What is the prognosis of post-partum thyroid dysfunction?

Answer 27

In future pregnancies, 25% of women may experience recurrence, and up to 30% of women may develop permanent hypothyroidism within 10 years. If treatment is withdrawn, annual TSH measurements are essential.

Question 28

What should be assessed in women with possible post-partum depression?

Answer 28

All women with possible post-partum depression should be assessed for thyroid dysfunction.

Question 29

What is the clinical practice point for women with post-partum thyroiditis?

Answer 29

All women with post-partum thyroiditis should have annual TFTs to look for hypothyroidism.

Question 30

When should thyroid function be checked in women at increased risk of thyroid dysfunction?

Answer 30

Thyroid function should be checked in early pregnancy and post-partum in all women at increased risk of thyroid dysfunction, such as those with underlying DM, autoimmune disorders, previous treatment with alemtuzumab, and checkpoint inhibitors.