Age-related patterns of thyroid-stimulating hormone response to thyrotropin-releasing hormone stimulation in Down syndrome
T. Sharav, H. Landau, Z. Zadik and T. R. Einarson
Jerusalem Child Development Center, Israel.
Thyroid function in subjects with Down syndrome was studied using the
thyrotropin-releasing hormone test. Forty-seven infants and children with
Down syndrome were investigated. Ages ranged from 1 month to 7 years; there
were 26 boys and 21 girls. Fourteen of the subjects with Down syndrome who
had an exaggerated thyroid-stimulating hormone response to
thyrotropin-releasing hormone stimulation had two or more annual follow-up
tests. The remaining 33 subjects who only underwent one
thyrotropin-releasing hormone test were compared with 22 age-matched
controls (11 boys and 11 girls). Mean basal thyroxine 4 and
triiodothyronine 3 values were in the normal ranges. All thyroid antibody
titers were negative. Mean basal thyroid-stimulating hormone levels of
subjects with Down syndrome were significantly higher than those of
controls for all ages, even though there was a decline in
thyroid-stimulating hormone levels in both groups. Peak thyroid-stimulating
hormone response levels were significantly greater in the subjects with
Down syndrome than in the controls. Longitudinal study of the 14 children
with Down syndrome with an exaggerated thyroid-stimulating hormone response
showed that the response remained exaggerated until the third year of life,
when it declined to normal levels. Thyroid dysfunction during the growth
spurt of infancy or delayed maturation of the hypothalamic pituitary
thyroid axis are proposed mechanisms.
