Author(s): Nasir A. M. Al-Jurayyan, Rushaid N. A. Al-Jurayyan, Aisha M. S. Al Senani
Results of a treatment strategy using an initial dosage of 10 – 15 μg/kg/day of L-thyroxine was evaluated in a prospective longitudinal study in King Khalid University Hospital, Riyadh, Saudi Arabia. Thyroid-stimulating hormone (TSH) and free-thyroxine (FT4) measurements being taken at 3 weeks, 6 weeks, 3 months, 6 months, 9 months and one year of the start of therapy. Forty-two newborns with confirmed primary congenital hypothyroidism (CH), detected by neonatal screening, were treated with the same therapeutic strategy (10 – 15 μg per kg per day). Twenty-one (50%) ectopic, 13 (31%) athyreotic, and 8 (19%) eutopic with in-creased uptake. A mean L-thyroxine dosage of 11.3 μg per kg per day (range 9.7 – 14.7) at the onset of treatment, normalized the FT4 (9-30 Pmol/L) levels at three weeks in 100%, and TSH (<10 mU/L) levels at six weeks in 90.5% of cases. However, hyperthyroxinaemia, FT4 levels ranging from 38 to 55 Pmol/L, was observed in six (14.3%) patients of different aetiology, which required modification in the doses given. They were initially started on higher dosages (12.3 – 14.7 μg per kg per day). Although an empirical initial dosage of 10 – 15 μg per kg per day of L-thyroxine is adequate and rapid in normalizing the thyroid status of infants with congenital hypothyroidism detected by neonatal screening, many infants who were started on higher dosages (12.3 – 14.7) showed elevated levels of FT4 which could expose infants to a dan-gerous hyperthyroidism, therefore, an initial lower dosage of 10 – 12 μg per kg per day of L-thyroxine with frequent and close monitoring of doses, and FT4, andTSH levels is more appropriate and saver than the currently recommended dosage of 10 -15 μg per kg per day for he initial treatment of infants with congenital hypothyroidism.