Clonidine Therapy for Short Stature: Can the Question Be Put to Rest?

Abstract

THE PERSISTENTQUESTION Should clonidine be used to ac­ celerate growth in children with short stature? is critically addressed by Toy and Middleton. As they point out, the factors affecting linear growth are complex and incom­ pletely understood. It is clear, however, that one important factor required for normal growth is the adequate release of pituitary growth hormone (GH). Since its discovery in 1979 as a useful pharmacologic agent to stimulate pituitary GH release,' the selective alpha.-adrenergic agonist cloni­ dine has been used extensively to acutely measure pituitary GH-producing capabilities. This property of clonidine has also raised substantial interest regarding its use for the treatment of short stature. The mechanisms by which clo­ nidine exerts this effect on GH release remain unknown, but are believed to be a result of direct stimulation of GH­ releasing hormone.! Many uncontrolled studies reviewed by Toy and Mid­ dleton have described a relationship between short-term clonidine administration and an increase in patient growth velocity. In addition, Volta et al. recently reported the re­ sults of their controlled, randomly assigned study that com­ pared the effects of placebo, levodopa, GH, and clonidine on growth velocity in children. These investigators demon­ strated an overall increase in the growth velocity for the six-month study period in children who received GH or clonidine. However, there appeared to be only a small per­ centage of individuals treated with clonidine (20 percent) who demonstrated an increased height velocity greater than 2 crn/y compared with controls.' In another recently published study, Esteban et al. concluded that clonidine in­ creased growth velocity >2 crn/y in 65 percent of 88 chil­ dren studied.' Nevertheless, and despite the opinions of