Thyroid Disease Flashcards
What are the clinical features of hyperthyroidism?
Heat intolerance, tachycardia, palpitations, palmar erythema, emotional lability, vomiting, goitre
Discriminatory features in pregnancy
- weight loss, tremor, persistent tachycardia, lid lag, exophthalmos
What is the most common cause of hyperthyroidism in pregnancy?
Graves (95%)
Other causes
- toxic multinodular goitre
- toxic adenoma
- thyroiditis
- iodine, Amiodarone, lithium therapy
What is the effect of pregnancy on hyperthyroidism?
T1 - exacerbation due to hCG
T2 and T3 - State of relative immunosuppression
Puerperium - exacerbations due to reversal of the fall in antibody levels
What is the effect of hyperthyroidism in pregnancy?
Maternal:
- Miscarriage
- IUGR
- PTL
- Perinatal mortality
- Palpitations: sinus tachy, SVT, AF
- Thyroid storm
- Heart failure
- If goitre: tracheal obstruction, dysphagia
Fetal:
- Fetal or neonatal thyrotoxicosis
What are the anti-thyroid drugs used to treat Grave’s disease and their adverse effects?
PTU:
- Neutropenia, agranulocytosis
- Liver failure
- Fetal hypothyroidism and goitre at high doses
Carbimazole:
- Neutropenia, agranulocytosis
- Aplasia cutis (absent patches of skin most often on scalp)
- Fetal hypothyroidism and goitre at high doses
How would you treat sympathetic symptoms of hyperthyroidism (i.e. tachycardia, sweating, tremor, palpitations)?
Metoprolol or propranolol (beta-blocker).
Can be discontinued after anti-thyroid drugs take effect usually within 3 weeks.
What is the best time to perform a thyroidectomy in pregnancy?
What are three indications for such treatment?
Second trimester
Dysphagia or stridor related to a large goitre
Confirmed or suspected carcinoma
Allergies to both anti-thyroid drugs
What is the risk of radioiodine therapy in pregnancy?
Fetal thyroid ablation and hypothyroidism
As the radioioidine is taken up by the fetal thyroid
What is the pathogenesis of neonatal / fetal thyrotoxicosis?
Transplacental passage of thyroid-stimulating antibodies
Most common in those with active disease in the third trimester
Can occur in mothers with a past history of Grave’s
What are the clinical features of neonatal / fetal thyrotoxicosis?
Tachycardia, irritability, jitteriness, poor feeding, goitre, hyperexcitability, hepatosplenomegaly, stare and eyelid retraction
Severe cases: congestive cardiac failure
What are clinical features of hypothyroidism?
Weight gain, lethargy, tiredness, Goitre
Hair loss, dry skin, constipation
Carpal tunnel syndrome, fluid retention
Discriminatory features in pregnancy: cold intolerance, slow pulse rate, delayed relaxation of the tendon
What are your differential diagnoses for hypothyroidism?
- Hashimoto’s thyroiditis (most common cause)
- Autoimmune destruction of thyroid with associated goitre.
- Following radioactive iodine treatment for hyperthyroidism
- Radiation exposure to thyroid
- Previous thyroidectomy
What is the effect of hypothyroidism on pregnancy?
Miscarriage
Anaemia
Fetal loss
PET
LBW
What are the clinical features of cretinism?
What it its cause?
Deaf mutism, spastic motor disorder, hypothyroidism
Severe maternal iodine deficiency causing permanent brain damage
With a thyroid nodule, what are the features indicating malignancy?
Previous history of radiation to the neck or chest in childhood
Fixation of the lump
Rapid growth of a painless nodule
Lymphadenopathy
Voice change
Horner’s syndrome
Raised thyroglobulin titre is suggestive of malignancy, as 90% of thyroid cancers secrete thyroglobulin
For women with a personal history of thyroid disease or symptoms of thyroid disease, what blood tests should they have on booking?
TSH
Free T4
How is overt hypothyroidism in pregnancy diagnosed?
TSH above reference range with a decreased T4
OR
TSH > 10mIU / L (regardless of T4)
What are the maternal risks in overt hypothyroidism?
PET
Anaemia
PPH
Anovulation + Miscarriage
What are the fetal risks in overt hypothyroidism?
Placental abruption
Prematurity
Perinatal mortality
Developmental delay
Outline your management of a woman with overt hypothyroidism in pregnancy:
Pre-pregnancy:
- TFTs
Antenatal:
- Thyroid peroxidase (TPO) antibodies if TSH >2.5 mU/L.
- Thyroid replacement therapy with thyroxine if TSH > than reference range with decreased free T4 OR TSH >10 mIU/L regardless of free T4 level. Approx 100-200 mcg/day.
- Explain low risk of fetal hyperthyroidism as very little thyroxine crosses placenta.
- Monitor TSH level at least once per trimester. Maintain maternal serum TSH within lower half of trimester specific pregnancy ranges.
- Recheck TSH 4-6 weeks after any thyroid dose changes.
Postpartum:
- Check TSH; if thyroxine dose increased in pregnancy at risk of hyperthyroidism/overreplacement.
What are the adverse effects of overt hypothyroidism on fetal development?
• Neuro cretinism
• Low IQ
• Low BW
• Neurodevelopment delays
Myxedematous cretinism
How do you identify pregnancies at risk of fetal thyrotoxicosis?
Previous or current maternal Graves’ disease with high TRab titres or levels that do not fall with advancing gestation.
Maternal TRab levels should be performed each trimester and at risk fetuses should undergo serial USS for assessment of fetal growth, fetal heart rate and fetal neck for goitre.
How long should neonatal thyrotoxicosis be treated?
How long should treatment continue for and why?
Neonatal thyrotoxicosis should be treated with anti-thyroid drugs ASAP. These are continued for a few weeks as maternal TRab are cleared the thyrotoxicosis will resolve.
Explain to a woman what Graves disease is, its effects on pregnancy and the effects of pregnancy on Graves disease:
Graves disease is an autoimmune condition where antibodies stimulate the TSH receptors on the thyroid causing excessive production of thyroid hormone.
Maternal effects of Graves disease:
- Miscarriage
- Cardiac arrhythmias: sinus tachy, SVT, AF.
- Thyroid crisis and heart failure
- If significant goitre: mass effect symptoms such as tracheal obstruction and difficulties swallowing.
Fetal and neonatal effects:
- Growth restriction
- PTL
- Perinatal mortality
- Fetal and neonatal thyrotoxicosis associated with increased fetal and neonatal mortality.
Effect of pregnancy on Graves disease:
- Severity often improves in 2nd and 3rd trimesters due to relative immunosuppression so lower requirements for antithyroid treatment.
- Can be worse in the first trimester due to hCG cross-reactivity and postpartum.
