Sm. Pueschel, GROWTH-HORMONE RESPONSE AFTER ADMINISTRATION OF L-DOPA, CLONIDINE, AND GROWTH-HORMONE RELEASING HORMONE IN CHILDREN WITH DOWN-SYNDROME, Research in developmental disabilities, 14(4), 1993, pp. 291-298
We studied the response of growth hormone secretion after the administ
ration of L-dopa, clonidine, and growth hormone releasing hormone in e
ight growth-retarded children with Down syndrome aged f to 6.5 years.
After L-dopa administration, five children had low growth hormone secr
etion (M = 3.7 ng/ml, SD - 2.12 at 30 min) and three children had elev
ated growth hormone levels (> 30 ng/ml). After clonidine administratio
n, six children had relatively low growth hormone levels (M = 3.15 ng/
ml, SD - 2.53 at 60 min) and two children had high levels (3&3 ng/ml a
nd 16.8 ng/ml, respectively). There was a better response after growth
hormone releasing hormone administration; only one child had a growth
hormone level of < 10 ng/ml. Most of the children had a modified resp
onse of growth hormone secretion subsequent to the various stimulation
tests. All children, however were able to secrete some growth hormone
(greater-than-or-equal-to 10 ng/ml) at kast during one of the stimula
tion tests. In comparison with peak growth hormone levels reported in
normal children our cohort had significantly lower growth hormone leve
ls only after clonidine administration. It is postulated that children
with Down syndrome have both anatomical and biochemical hypothalamic
derangements that may result in decreased growth hormone secretion and
reduced linear growth In addition, other mechanisms that may be in pa
rt responsible for the observed growth retardation are discussed.