Thyroid disease in pregnancy

Question 1

Discuss normal physiologic changes found in the thyroid during pregnancy

Answer 1

• Significant increase in metabolic demands during pregnancy
• hCG acts as a weak thyroid stimulating hormone
• 1st tri → increase in T4 with rising hCG
• Increase in thyroxine-binding globulin → significant increasein total (but not free) T3 and T4.
  
  • Levels increase until 20 weeks and then plateau and remain steady for 2nd half of pregnancy.
• 30% increase in volume by term

Question 2

Define normal levels of thyroid hormones during pregnancy:

Thyroxine (T4), free

(ng/dL)

Answer 2

0.3 - 1.58​

• 1st tri - 0.7 - 1.58
• 2nd tri - 0.4 - 1.4
• 3rd tri - 0.3 -1.3

Question 3

Define normal levels of thyroid hormones during pregnancy:

Thyroxine (T4), total

(µg/dL)

Answer 3

​3.5 - 9

• 1st tri - 3.6 - 9
• 2nd tri - 4.0 - 8.9
• 3rd tri - 3.5 - 8.6
• Term - 3.9 - 8.3

Question 4

Define normal levels of thyroid hormones during pregnancy:

Triiodothyronine(T3), total

(ng/dL)

Answer 4

71 -214

• 1st tri - 71 - 175
• 2nd tri - 84 - 195
• 3rd tri - 97 - 182
• Term - 84 - 214

Question 5

Define normal levels of thyroid hormones during pregnancy:

Triiodothyronine (T3), free

(pg/mL)

Answer 5

​2.1 - 4.4

• 1st tri - 2.3 - 4.4
• 2nd tri - 2.2 - 4.2
• 3rd tri - 2.1 - 3.7
• Term - 2.1 - 3.5

Question 6

Define normal levels of thyroid hormones during pregnancy:

TSH

(µIU/mL)

Answer 6

• 1st tri - 0.1 - 4.4
• 2nd tri - 0.4 - 5
• 3rd tri - 0.23 - 4.4
• Term - 0 - 5.3

Question 7

Hyperthyroidism

Signs and Symptoms

Answer 7

• 90% caused by Graves Disease (autoimmune)
• Some symptoms may mimic physiologic pregnancy:
  • Warm skin
  • Palpitations
• Other symptoms:
  
  • Tachycardia
  • Thyromegaly
  • Exophthalmos
  • No weight gain
  • Frequent stools
  • Insomnia
  • Nervousness
• Low / 0 TSH with elevated T4
• Antibody assays for prediction of fetal thyroid dysfunction

Question 8

Gestational Thyrotoxicosis

Answer 8

• HyperemesisGravidarum
  
  • Elevated hCG levels can cause transient hyperthyroidism
  • ARD’s are not indicated
• Gestational Trophoblastic Disease
  
  • Thyrotoxicosis present in 25 – 65% people with GTD
  • Related to elevated hCGlevels
  • Resolves with appropriate treatment of trophoblastic disease
• Multiple Gestations

Question 9

Thyroid storm

Answer 9

• Acute, life-threatening conditions → ICU
• Rare complication of hyperthyroidism in pregnancy
• Thyroxine has profound myocardial effects
  
  • Increase HR, cardiac contractility,and cardiac output, vasodilation
• Risk increases with other physiologic stressors:
  
  • Preeclampsia
  • Anemia
  • Sepsis
• Clinical dx:
  • Severe signs of thyrotoxicosis with significant hyperpyrexia (>103° F)
  • Neuropsychiatric symptoms
  • Tachycardia > 140 beats/min is not uncommon and congestive heart failure is a frequent complication.
  • GI sx such as nausea and vomiting

Question 10

Risks of poor control of hyperthyroidism

Answer 10

Parent:

• Preeclampsia
• Heart failure
• Preterm delivery
• Growth restriction
• Early pregnancy loss

Fetus:

Hyper or hypo thyroid +/- goiter

Hydrops

IUFD

Low birthweight

Question 11

Hypothyroidism

Signs and symptoms

Answer 11

• Some sx can mimic physiologic pregnancy symptoms:
  
  • Fatigue
  • Constipation
  • Weight gain
• Elevated TSH with low T4
• Complicates 2-10/1000 pregnancies
• Most common cause in US: Hashimoto thyroiditis
• Glandular destruction due to TPO antibodies
• Most common cause worldwide: iodine deficiency

Question 12

Risks of untreated hypothyroidism

Answer 12

• Parent
  
  • Placental abruption
  • Cardiac dysfunction
  • Preeclampsia
• Fetus
  
  • Impaired neurodevelopment
  • Low birthweight
  • IUFD

Question 13

Postpartum thyroiditis

Answer 13

• Thyroid dysfunction within 12 months of delivery
• Typical presentation: period of thyrotoxicosis followed by hypothyroidism
• Transient autoimmune thyroiditis prevalence 5-10%
• Diagnosis often missed
• Symptoms begin 1-4 months after delivery
  
  • Baby blues, anxiety, hair loss, fatigue often attributed by people and their providers to strain of parenting
  • Oftern goiter
• Generally self-limiting and resolves within 12-18 months
• In 20% of cases hypothyroidism will persist and require treatment

Question 14

Discuss the controversy regarding screening for thyroid disease in pregnancy

Answer 14

• ACOG, SMFM, etc. all agree: no TSH/TFT screening in low risk, asymptomatic pregnant people
• Thyroid antibody screening: an area for future study
• Testing should be performed in high risk or symptomatic patients
  
  • Family history of thyroid or autoimmune disorder
  • Personal history of another autoimmune disease
  • Personal history of thyroid disease or surgery
  • Personal history of radiation of neck

Question 15

Discuss the neonatal sequelae of hypothyroidism

Answer 15

Impaired neurodevelopment

Low birthweight

IUFD