In congenital hypothyroidism, an initial L-thyroxine dose of 10–12 μg/kg/day is sufficient and sometimes excessive based on thyroid tests 1 month later

Abstract

An initial L-T4 dose of 10-11.9 μg/kg for TSH>100 μIU/L and 8-10 μg/kg for TSH<100 μIU/L at diagnosis met and often exceeded the target thyroid levels at 1 month. More frequent overtreatment was seen when >12 μg/kg was given.

Targeted Levothyroxine Therapy for Treatment of Congenital Hypothyroidism

“…This is consistent with the findings of another study that reported more frequent OT 1 month after starting therapy when >12 mcg/kg was given (4). These authors suggested that initial LT4 doses of 10 to 11.9 mcg/kg for infants with a TSH >100 mcU/L and 8 to 10 mcg/kg for those with a TSH <100 mcU/mL are sufficient.…”

“…In children with congenital hypothyroidism (CH), early identification and treatment with high-dose levothyroxine (LT4) at 10 to 15 mcg/kg daily has been shown to rapidly normalize thyroid-stimulating hormone (TSH) levels and improve neurodevelopmental outcomes (1,2). However, the risk of inducing supraphysiologic thyroxine levels increases with higher initial doses of LT4 (3,4). Several studies have suggested that this might also be harmful to the developing brain, and episodes of over-treatment (OT) have been linked to a difficult temperament in infancy, as well as lowered intellectual functioning and decreased attention span later in childhood (3,5,6).…”

Levothyroxine replacement in primary congenital hypothyroidism: the higher the initial dose the higher the rate of overtreatment

“…In the present study, we evaluated the effects of initial L-thyroxine doses on patients with CH and found that the rate of overtreatment at the first month is significantly higher in the high-dose group. Similarly, Vaidyanathan et al (6) reported an overtreatment rate of patients who received 12-15 μg/kg/day of LT4 as an initial dose, which was higher at the first month compared with groups receiving 10-11.99 μg/kg/day and 6-9.9 μg/kg/day at month 1 (75%, 55% and 37.5%, respectively).…”

“…In the study performed by Vaidyanathan et al in 55 patients (6), they revealed that infants with a TSH level of 100 μIU/L or higher received a mean LT4 dose of 12.6 μg/kg/day and had higher rates (71%) of overtreatment. They also reported that a lower dose of LT4 (8-10 μg/kg/day) could be sufficient in infants with less severe CH (TSH: 20-100 μIU/L).…”

“…The target ranges for TSH and fT4 at end of 1 month of therapy were defined as 0.5-6 μIU/L and 1.1 -2.3 ng/dL, respectively. Patients with fT4 < 1.1 ng/dL±TSH > 6 μIU/L at month one were considered to have undergone undertreatment, while patients with fT4 > 2.3 ng/dL±TSH < 0.5 μIU/L were considered to have undergone overtreatment (6).…”