A case of hypothyroidism in infancy

Patient X was investigated at 6 months of age for weight gain. She was born on the 9th centile at 35 weeks and was between the 25th and 50th centile at 6 months, with length below the 0.4th centile (see growth chart). She had no obvious dysmorphic features or family history of note. Her newborn screening thyroid-stimulating hormone (TSH) result was normal. Current thyroid function tests (TFTs) at 6 months of age are shown below: TSH: 15.98 (reference range 0.35–5.00) mU/L Free T4: 8.1 (reference range 9.0–21.0) pmol/L Thyroid antibody testing: Negative 1. On assessment in clinic you notice that her weight has further increased by 1.5 kg in 4 weeks (see growth chart in figure 1). Figure 1 Weight cart. What do you do? 1. Give dietary advice 2. Repeat TFTs and start on …