Thyroid disease in diabetes

Question 1

thyroid disease physiology (3)

Answer 1

Hypo- and hyperthyroidism causes anovulatory cycles – reduced fertility

Maternal thyroxine important for neonatal development (especially CNS)

Increased demand on thyroid during pregnancy
Plasma protein binding increases

Question 2

Hypothyroidism in pregnancy (5)

Answer 2

Pre-existing hypothyroidism

-Unable to compensate for increase demand
-Increase thyroxine dose by 25mcg AS SOON AS pregnancy suspected
-Check TFTs monthly for first 20 weeks then 2 monthly until term
-The average dose increase is by 50% (e.g. from 100mcg to 150mcg) by 20 weeks.
-Aim for TSH <3-4 mU/l

Question 3

Untreated Hypothyroidism – the risks (7)

Answer 3

Increased abortion, preeclampsia, abruption, postpartum haemorrhage, preterm labour,

Foetal neuropsychological development

Untreated hypothyroid mothers vs. normal mothers:
-Average of 7 IQ points less in children
-Increased risk of IQ < 85 (19% vs. 5%)

Question 4

hCG

Answer 4

increases thyroxine

supresses tsh

Question 5

hCG and TSH have two chain peptides:

Answer 5

a- chain identical
b-chain different

Question 6

High hCG

Answer 6

-high free t4
-low TSH
-hyperemesis
-High hCG mimics Hyperthyroidism biochemically, symps of weight loss and nausea can be similar also

Question 7

Low TSH/High free T4 in pregnancy- What is the cause (5)

Answer 7

hCG effect (a TSH like effect)
-fT4 increased (14% of pregnancies)

-Low TSH (0.1-0.4) 9% of pregnancies

-Hyperemesis gravidarum– hCG HIGH, 50% have low TSH (±↑fT4)

Excess hCG effect mimics hyperthyroidism biochemically

Question 8

Thyrotoxicosis & Pregnancy- causes (3)

Answer 8

-Graves’ disease
-TMNG, toxic adenoma
-Thyroiditis

Question 9

Hyperthyroid Management in Pregnancy (9)

Answer 9

Wait and see (supportive management)
- if hyperemesis, will settle
- Graves’ may settle as preg suppresses autoimmunity - Check TRAB antibodies

B-blockers if needed (short term)

LOW DOSE anti-thyroid drugs
- Propylthiouracil 1st trimester
- Carbimazole 2/3rd trimester
- wait as late as possible

Question 10

Antithyroid drugs (2)

Answer 10

-carbimazole
-propylthiouracil

Question 11

CARBIMAZOLE (4)

Answer 11

-Can cause embryopathy in 1st trimeter
-Scalp abnormalities
-GI abnormalities
-Choanal & Oesophageal atresia

Question 12

PROPYLTHIOURACIL (3)

Answer 12

-Can cause embryopathy but risk thought to be less
-Risk of liver toxicity
-Best avoided except possibly in 1st trimester, but then switch to CBZ

Question 13

TRAb antibodies in Pregnancy (3)

Answer 13

-Check TRAb antibodies during pregnancy (ideally third trimester)
-If present alert neonatalogist
-TRAb antibodies can cross the placenta and cause neonatal transient hyperthyroidism and thyroid disease

Question 14

Postpartum Thyroiditis (7)

Answer 14

-5% (3-16%) postpartum women (25% in T1DM)
-Transiently thyrotoxic= Hypothyroid
-Can persist up to 1 year postpartum
-25-50% persistent hypothyroidism beyond 1 year
-Small, diffuse, nontender goitre
-Hypothyroid phase assoc with postnatal depression
-Postpartum =Exacerbation of all autoimmune dx