Endocrine complications in pregnancy

Question 1

What are some of the metabolic changes which take place in pregnancy?

Answer 1

• Increased erythropoeitin, cortisol and noradrenaline
• High cardiac output
• Plasma volume expansion
• High cholesterol and triglycerides
• Hyperventilation
• Pro-thrombotic and inflammatory state
• Insulin resistance

Question 2

Until when is the foetus dependent on maternal T4 for?

Answer 2

During first trimester as foetal thyroid follicles begin to develop at 10 weeks gestation
Foetal T4 takes over in 2nd trimester

Question 3

What are glycoprotein hormones?

Answer 3

Family of hormones including TSH, LH, FSH, hCG

They contain common alpha subunit and distinct B subunit.

Question 4

What happens to thyroxin binding globulin (TBG) in the first trimester and what effect does this have on T4 levels?

Answer 4

It increases due to oestrogen

This will increase T4 levels

Question 5

What effect does hCG have on the thyroid?

Answer 5

In high levels, it stimulates the TSH receptor and therefore, increases T4 levels

Question 6

What happens to thyrotrophin levels during pregnancy?

Answer 6

They decrease due to an increase in free T4 levels

Question 7

Do thyroid hormones and TSH receptor antibodies cross the placenta?

Answer 7

Yes -

But there is no transfer of maternal TSH across the placenta

Question 8

Why is it important to manage thyroid levels during pregnancy?

Answer 8

Thyroid hormone is crucial for embryogenesis and foetal development

Question 9

Is hypo or hyper thyroidism more common during pregnancy? What should we do?

Answer 9

Hypothyroidism (2-3%)

We should icnrease thyroxin dose if they suspect they are pregnant and have thyroid levels checked as soon as pregnancy is confirmed.
If TSH levels are low = investigate and look for thyrotoxicosis
If TSH between 0.1-2.5 then this is normal and no need to investigate or treat
If TSH between 2.5-10 they require further assessment looking for TPOAb - marker for autoimmunity
TPOAb positive = levothyroxine
TPOAb negative = less likely to be treated with levothyroxine
If TSH >10 = start treatment. with levothyroxine and measure TFT at 4-6 weeks

Question 10

What effects can uncontrolled hypothyroidism have on the foetus during pregnancy?

Answer 10

1. Gestational HTN and pre-eclampsia
2. Placental abruption
3. Post-partum haemorrhage
4. Low birth weight
5. Pre-term delivery
6. Neonatal goitre
7. Neonatal respiratory distress

Question 11

What is subclinical hypothyroidism, do we treat pregnant women with subclinical hypothyroidism?

Answer 11

When TSH is high but T3 and T4 are normal

We do not treat as there is no evidence there is an improvement with treatment in cognitive function etc.

Question 12

Who do we target screen for hypothyroidism in pregnancy?

Answer 12

Age >30
BMI >41
Miscarriage preterm labour
Personal or fam history of hypothyroidism
Goitre
T1DM
Head and neck irradiation
Amiodarone, lithium or contrast use

Question 13

What is the most common cause of hyperthyroidism?

Answer 13

Graves - 85-90%

Question 14

What are the effects of thyrotoxicosis on pregnancy?

Answer 14

1. IUGR
2. Low birth weight
3. Pre-eclampsia
4. Pre-term delivery
5. Risk of still birth
6. Risk of miscarriage
   Pregnancy also worsens graves in the 1st trimester and improves it in the latter half of the pregnancy

Question 15

How do we treat Graves in pregnancy?

Answer 15

Beta blockers for symptomatic treatment - propanolol
Antithyroid medication - propylthiouracil (PTU) - first line or carbimazole (2nd line)
Use lowest dose in pregnancy
PTU monitored as can cause rare hepatotoxicity
Surgical interventions (thyroidectomy) in 2nd trimester if woman does not tolerate treatment

Question 16

Can thyroid autoantibodies cross the placenta? Who do we test for Antibodies?

Answer 16

Yes and they can cause neonatal thyrotoxicosis

We test current Graves, past Graves and those with a previous neonate with Graves’

Question 17

How do we differentiate between Graves and Gestational thyrotoxicosis?

Answer 17

Graves = symptoms before pregnancy and worsened during 1st trimester with goitre and TSH-R antibody

Gestational thyrotoxicosis = Symptoms do not predate pregnancy, there may not be symptoms during pregnancy, no goitre and no TSH-R antibodies present

Question 18

How common in post-partum thyroiditis and who is at higher risk?

Answer 18

7% prevalence
High risk:
- T1DM
- Graves disease in remission
- Chronic viral hepatitis

Question 19

What are some drugs which cause changes in thyroid levels?

Answer 19

Amiodarone
Lithium
Interferon
Immune therpies

Question 20

Why does amiodarone cause thyroid dysfunction?

Answer 20

It has a high iodine content (37% by weight) and it is a lipid soluble drug so it has long lasting effects.
Amiodarone can cause Amiodarone induced Hypothyroidism more commonly and affects more females.
It usually occurs in patients with susceptibility to thyroid disease such as Hashimoto’s or those with positive antithyroid antibodies.
It has an inhibitory effect on thyroid hormone synthesis.