NHS Lothian neonatal guidelines (in development)- Tachycardia, arrhythmias, hydrops
- Hyperkinesis
- IUGR
- Goitre picked up on fetal ultrasound scan
- Advanced bone age may be detected on ultrasound of the lower femoral epiphysis
- Preterm delivery
- Death in utero
Identification and management of neonatal thyrotoxicosis
Warning
- The baby is more likely to be affected if the mother has received treatment during pregnancy.
- Known TSH receptor antibody titres in pregnancy: High risk is a titre approximately five times the upper limit of normal.
- Thyroid stimulating immunoglobulin levels from mothers in 3rd trimester, and the neonate correlate with risk of development of thyrotoxicosis.
- Thyroid stimulating immunoglobulin levels in neonate are predictive of the risk of hyperthyroidism (more so than maternal antibody titres but the result is not usually available in time to be of benefit to inform the neonatal management).
- Anomalies associated with the use of carbimazole (methimazole) in pregnancy are rare but include cutis aplasia, choanal atresia, gastrointestinal anomalies including oesophageal atresia, developmental delay, hearing loss, and dysmorphic facial features.
- Antithyroid drugs (propylthiouracil, carbimazole or methimazole) may cross the placenta and render the fetus hypothyroid. In contrast thyroxine only crosses the placenta in small amounts.
- Symptoms may be present at birth or delayed for several days (particularly if the mother is on antithyroid medication at time of delivery)
- Usually apparent by D10
- Can occur up to D45 after birth
- Goitre
- Central nervous system - Irritability, jitteriness, restlessness
- Periorbital oedema, lid retraction, exophthalmos
- Cardiovascular system – tachycardia, arrhythmia, failure
- Systemic and pulmonary hypertension
- Hypermetabolism - voracious appetite, diarrhoea, failure to thrive, flushing, sweating, tachypnoea
- Persisting acrocyanosis
- Hepatosplenomegaly, lymphadenopathy
- Thrombocytopaenia – petaechiae + bruising
- Craniosynostosis, advanced bone age, microcephaly
- Jaundice
It is not clear whether one should treat biochemical thryotoxicosis (fT4 above the normal range for age and TSH suppressed) in the absence of symptoms, but in practice most infants are treated. This is a consultant decision. Please discuss with Paula Midgley (any time of day or night). If Paula is away, then this should be discussed with the endocrine team at RHSC.
Immediate
Thionamide: The dosages as per BNFc. Lugol’s Iodine solution can be given if available.
- Thionamide: Either Propylthiouracil or Carbimazole
- As this may take 24-48 hours to have some effect, consider blocking release of thyroid hormones with iodine eg, Lugol’s solution
- Sympathomimetic effects may require β-blockade, for example Propranolol to control symptoms (beware side effects – bradycardia, hypotension and hypoglycaemia)
- Corticosteroids may be helpful for example Prednisolone if symptoms are severe
- Sedatives may be helpful
- Heart failure may require appropriate treatment.
- Thyrotoxicosis has been successfully treated with iodine-containing contrast media - Iopanoic acid or sodium ipodate
Medium term
- It is easy to over treat the thyrotoxic baby so beware of drug-induced hypothyroidism.
- The duration of thyrotoxicosis is determined by the persistence of maternal thyroid stimulating immunoglobulins in the baby’s blood. Thyrotoxicosis usually remits after 8-20 weeks, and virtually all babies are euthyroid by 48 weeks.
Longterm
- Once thyroid function normal off treatment, no further endocrine review required
- Follow-up of growth and development may be considered
- There is a risk of recurrence in future pregnancies
Thyroid Stimulating Hormone (TSH)
| Age | mU/L |
| Neonates <3 days | 1.3 – 25 |
| 3 days - 4 weeks | 0.7 – 7.4 |
| 4 weeks to 6 months | 0.7 – 6 |
Thyroxine, Free T4
| Age | pmol/L |
| Neonates <7 days | 13 - 34 |
| 7 - 14 days | 12 - 26 |
| 14 - 28 days | 12 - 23 |
| 4wks to 1 year | 11 - 19 |
TSH receptor antibodies (TRAB)
| All ages | < 1.6 IU/L |