title: Monitoring of growth hormone replacement therapy in adults, based on measurement of serum markers.
abstract: The optimal dose for GH replacement therapy in GH-deficient (GHD) adults is not known, nor is there a consensus as to which method is the most appropriate for the monitoring of treatment. To establish a general guideline for GH replacement therapy in adults, we evaluated the relationship between the administered GH dose and the achieved serum levels of three GH-dependent serum markers. Serum levels of insulin-like growth factor I (IGF-I), IGF-binding protein-3 (IGFBP-3), and the acid-labile subunit (ALS) were measured in 46 GHD men participating in a 1-yr, double blind, and placebo-controlled dose-response study. The doses of recombinant human GH ranged from 0.33-3.0 IU/m(2)-day. During GH treatment, dose reduction was necessary because of side-effects in 18 of 46 patients, i.e. in 18% of the patients receiving a maintenance dose of 1 IU/M(2)-day, in 35% of the patients receiving a dose of 2 IU/m(2)-day, and in 67% of the patients receiving a dose of 3 IU/M(2)-day. In the untreated state, serum levels of all three markers were below the normal range in 90% of the patients. The rise in serum marker concentrations during the first month of treatment was dose dependent. Significant increases in IGF-I, IGFBP-3, and ALS levels were observed with a dose as low as 0.33 IU/M(2)-day. The minimal GH dose required for normalization of the serum IGF-I concentration was 0.66 IU/M(2)-day, and it was 1.0 IU/M(2)-day for ALS and IGFBP-3. In patients receiving 2.0 IU/M(2)-day, the mean serum IGF-I concentration rose to an abnormally high level, whereas at this dose, the mean IGFBP-3 and ALS levels were not different from normal. The lower sensitivity of IGFBP-3 and ALS to GH doses in the high range was also apparent during long term treatment. The number of patients who developed IGFBP-3 or ALS levels that exceeded the upper normal limit was substantially smaller than the number of patients with elevated IGF-I concentrations (2, 8, and 19 of 46 patients, respectively). In conclusion, serum IGF-I appears to be the preferred biochemical marker for the detection of GH excess in adults receiving GH replacement therapy, because it is more sensitive than IGFBP-3 and ALS to GH doses in the high range. If normalization of the serum IGF-I concentration is taken as the criterion for optimal GH replacement therapy, the predicted optimal GH dose for GHD men 20 - 40 yr old is 1.4 IU/M(2)-day, and the 95% confidence interval is 1.2-1.6 IU/M(2)-day.
authors.affiliation: Department of Endocrinology, Free University Hospital, Amsterdam, The Netherlands.
authors.forename: H
authors.initials: H
authors.lastname: de Boer
authors.forename: G J
authors.initials: GJ
authors.lastname: Blok
authors.forename: C
authors.initials: C
authors.lastname: Popp-Snijders
authors.forename: L
authors.initials: L
authors.lastname: Stuurman
authors.forename: R C
authors.initials: RC
authors.lastname: Baxter
authors.forename: E
authors.initials: E
authors.lastname: van der Veen
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood*; D013196:Dihydrotestosterone / Q000097:blood; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D016903:Drug Monitoring; D005500:Follow-Up Studies; D013006:Growth Hormone / Q000009:adverse effects / Q000172:deficiency* / Q000627:therapeutic use*; D013007:Growth Hormone-Releasing Hormone / Q000097:blood; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000032:analysis; D046911:Macromolecular Substances; D008297:Male; D010919:Placebos; D013739:Testosterone / Q000097:blood; D013974:Thyroxine / Q000097:blood; D013997:Time Factors; D014284:Triiodothyronine / Q000097:blood
chemical_list: D015415:Biomarkers; D018972:Insulin-Like Growth Factor Binding Protein 3; D046911:Macromolecular Substances; D010919:Placebos; D014284:Triiodothyronine; D013196:Dihydrotestosterone; D013739:Testosterone; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone; D013974:Thyroxine