Factors involved in the rate of fall of thyroid stimulating hormone in treated hypothyroidism

Abstract

The rate of fall of serum thyroid stimulating hormone (TSH) concentrations in 32 hypothyroid infants (11 boys, 21 girls) was studied after starting treatment with thyroxine to determine whether it was influenced by initial TSH concentration or the cause of the hypothyroidism. Of 27 patients who had isotope scans before treatment was started, 11 (40%) were athyrotic, 10 (38%) had an ectopic gland, and six (22%) probably had dyshormonogenesis. Treatment was started with thyroxine at 100 µg/m 2 /24 hours at a mean age of 26 days (range 14-45). Serum TSH concentrations remained increased in 26 (81%) at 3 months, 20 (62.5%) at 6 months, and nine (28%) at 1 year and beyond. The mean age for serum TSH to reach the normal range was 0.79 years (range 0.15-2.1 years). Diagnosis (in 27 patients) and initial results (in 32) made no diVerence to the rate of fall.

Persistence of Mild Hyperthyrotropinemia after Discontinuation of Three-Year Course of Low-Dose L-Thyroxine Therapy in Infants with Borderline Hypothyroidism

“…For the children with hypothyroidism, the Japanese Society for Pediatric Endocrinology recommends giving 5 to 7 mg/kg/d at the age of 1 to 5 years [7], hence the dosage applied in our study is less than this recommendation. As for follow-up treatment, Raza et al reported that maintaining serum FT4 levels within the normal range, regardless of TSH concentration, is the safest approach in treating congenital hypothyroidism [8].…”

Suppression of TSH in Congenital Hypothyroidism Is Significantly Related to Serum Levels and Dosage of Thyroxine

“…We do not have data on the aetiology of CH for our patients. Some studies have found no difference in serum T 4 and TSH levels during treatment of CH infants with different aetiologies [8, 14, 15], whereas others found significant differences in the time to TSH suppression in athyrotic infants as compared with infants with ectopic/hypoplastic glands or dyshormonogenesis [20, 23]. …”

“…In their cohort, treatment was started later, at a mean age of 45 days, and 47 infants were excluded who failed to meet their stringent inclusion criteria. When hypothyroid infants were treated with a lower T 4 dose (100 µg/m 2 /day, about 6.7 µg/kg/day), only 19% had suppressed TSH levels by 3 months (<6 mU/l) [8]. Abusrewil et al [9], treating infants with a variety of initial doses of T 4 , reported an intermediate number of suppressed cases at corresponding ages.…”

“…Some authors [8]maintain that early normalization of serum T 4 levels, independent of the corresponding TSH concentrations, is a satisfactory treatment goal, whereas others [11, 12]have emphasized that the TSH level is the only biological marker of adequacy of tissue levels of T 4 , particularly in the brain. Proponents of management based on T 4 levels alone raise concerns about short-term side effects of overtreatment [8]and long-term neuropsychological sequelae [13], such as poor concentration with larger doses of T 4 . Advocates of early TSH suppression assert that rapid correction of fetal hypothyroidism is required to close the IQ gap between children with severe CH and normal controls [7].…”

“…In monitoring the effects of T 4 replacement, a delay in thyrotropin (thyroid-stimulating hormone; TSH) suppression has often been documented [8, 9]. Whether this is due to abnormalities in the hypothalamic setpoint for inhibition of TSH release by T 4 [10]or undertreatment has not been resolved.…”