Introduction <p>Congenital hypothyroidism, which is screened for on the national newborn bloodspot screening test, has potentially devastating developmental consequences for a child if left untreated. The disease may be otherwise innocuous in a newborn with symptoms including fatigue, poor feeding and constipation. Outside of the need for supplemental levothyroxine, an ectopic thyroid gland and hemi-agenesis bear no additional risk to the individual once identified and treated.</p> Case report <p>Congenital hypothyroidism was detected in an otherwise asymptomatic neonate on the newborn heel-prick screening test. Confirmatory serum analyses of both the infant and mother were performed. Thyroid scintigraphy and thyroid ultrasound confirmed the absence of an orthotopic thyroid gland, with a solitary ectopic thyroid lobe detected sublingually. The infant was started on supplemental levothyroxine and titrated until serum thyroid levels normalised. Developmental milestones and serial parameters, including weight, height, and head circumference, were normal.</p> Discussion <p>Congenital hypothyroidism, which is screened for on the national newborn bloodspot screening test, has potentially devastating developmental consequences for a child if left untreated. The disease may be otherwise innocuous in a newborn with symptoms including fatigue, poor feeding and constipation. Outside of the need for supplemental levothyroxine, an ectopic thyroid gland and hemi-agenesis bear no additional risk to the individual once identified and treated.</p>