Q. What are the indications for the use of GnRH agonist? How it should be given ?
A. The use of drugs in the idiopathic form of TPP is influenced by the age of onset of symptoms and rapidity of progression. When CPP is rapidly progressive and occurs in a young child with the possibility of compromising height potential, the best form of medical therapy available today is with GnRH agonist. Chronic administration of these compounds down regulates and desensitizes GnRH receptors on pituitary gonadotropes. This leads to inhibition of gonadotropin release followed by decreased secretion of sex steroids. Depending on the nature of the preparation, GnRH can be administered by the SC route or intranasally daily or in a long acting repository form every 4 weeks. Within 2-4 weeks of adequate treatment with these agonists, the mean LH response to GnRH is within the prepubertal range and the sex steroid levels are suppressed by 4-12 weeks. The secondary sex characters regress and the accelerated growth velocity and bone age advance are slowed during the first year of therapy.

Leuprolide Acetate (Lupron depot ped) is the only depot preparation approved in USA and is given as 0.25 to 0.3 mg/kg, minimum 7.5 mg IM once in 4 weeks. Triptorelin available here as (Decapeptyl) is used in doses of 60 to 75 mcg/kg IM once in 3 to 4 weeks. Aqueous daily S.C. injection of leuprolide 50 mcg/kg twice a day or intranasal nafarelin (Synarel) 800 mcg bid are other preparations.

Therapy should be monitored in these children at regular intervals, with gonadotropin and sex steroid levels maintained in prepubertal range in both the sexes. Skeletal maturation is retarded to a greater degree than linear growth with resultant increase in prediction for adult stature. Occasional allergic reaction may occur otherwise no toxic reactions are reported. Medical therapy is advisable for nonprogressive neurogenic lesions causing CPP including postmeningitic forms or hamartomas.