Subcutaneous degradation of biosynthetic human growth hormone in growth hormone deficient patients

The aim of the present study was to look further into the question of local degradation of sc injected human GH in GH deficient patients. A comparison was made of serum GH levels after constant iv and sc infusion of the same amount of GH (33 ng.kg-1.min-1) in the same 9 GH deficient patients. A 3-h lag period was interposed between the iv and the sc infusion. Iv infusion was continued for 3 h. All 9 subjects subsequently received sc infusion for 19 h and five of them continued for additionally 24 h. The mean steady state serum GH level in the nine patients was 23.1 +/- 5.1 micrograms/l after iv and 6.8 +/- micrograms/l after sc administration (P less than 0.01). Extension of the sc infusion period in 4 of the subjects did not significantly alter the serum GH level (P less than 0.15), implying that a steady state was reached. The GH in the infusion system was stable throughout a 24-h period. We therefore conclude that sc injected GH is degraded locally to a substantial extent.