Major finding: With use of four criteria to help determine whether to monitor infants with congenital hypothyroidism, monthly monitoring was deemed required in 75% of children in the first 6 months of life and in 35% during the second 6 months.
Source of data: A retrospective chart review of 70 infants seen at a single institution.
Disclosures: Dr. Balhara stated that she had no relevant financial disclosures
NEW YORK — Monthly monitoring of thyroid status was justified in 75% of 70 infants with congenital hypothyroidism in the first 6 months of life and for 35% of those infants in the next 6 months, in a retrospective chart analysis.
The findings suggest that monthly monitoring should continue for a year in all infants with congenital hypothyroidism, in contrast to current guidelines stating that serum T4 and TSH measurements should be performed every 1–2 months during the first 6 months of life, followed by 3- to 4-month intervals from 6 to 36 months of age.
The 2006 guidelines, issued jointly by the American Academy of Pediatrics, the American Thyroid Association, and the Lawson Wilkins Pediatric Endocrine Society, also advise a repeat test at 4 weeks after any change in levothyroxine dosage, and “more frequent intervals” when compliance is questioned, abnormal values are obtained, or the dose or source of medication has been changed (Pediatrics 2006;117:2290–303).
“There is a paucity of literature behind the AAP recommendation. We monitor more frequently in the second 6 months of life. Based on our results, we think [infants with congenital hypothyroidism] need monthly monitoring for the entire first year,” Dr. Bharti Balhara said in an interview during her poster presentation at a joint meeting of the Lawson Wilkins Pediatric Endocrine Society and the European Society for Pediatric Endocrinology.
The 70 patients were among 98 who were seen at the pediatric endocrine unit of Massachusetts General Hospital for Children, Boston, where Dr. Balhara works. She and her associates developed the following four criteria to indicate the need for monthly monitoring:
▸ Dose change within a month of previous visit.
▸ Total/free T4 levels not in the upper half of normal within a month of previous visit.
▸ TSH more than twice the upper limit of normal 2 months after a visit (if monitoring was done every other month) associated with total/free T4 not in the upper half of normal range.
▸ Any TSH below 0.1 microIU/mL.
Based on those criteria, monthly monitoring was required in 75% of children in the first 6 months of life and in 35% during the second 6 months. Children who required monthly monitoring in the second 6 months of life had higher baseline TSH (326 vs. 192 microIU/mL) and lower baseline total T4 (5.6 vs. 7.8 mcg/dL), compared with those who did not require it.
Variables found not to predict the need for monthly monitoring included baseline levothyroxine dose, ethnicity, sex, birth weight, or prematurity. Also not significant was thyroid dysgenesis, Dr. Balhara reported.