title: Impact of Growth Hormone on Cystatin C.
abstract: BACKGROUND
  Cystatin C (CysC) is an alternative marker to creatinine for estimation of the glomerular filtration rate (GFR). Hormones such as thyroid hormones and glucocorticoids are known to have an impact on CysC. In this study, we examined the effect of growth hormone (GH) on CysC in patients with acromegaly undergoing transsphenoidal surgery.
  
  
  METHODS
  Creatinine, CysC, GH and insulin-like growth factor-1 (IGF-1) were determined in 24 patients with acromegaly before and following transsphenoidal surgery. Estimated GFR was calculated using the Chronic Kidney Disease Epidemiology Collaboration formula.
  
  
  RESULTS
  In all patients, surgical debulking resulted in decreased clinical disease activity and declining GH/IGF-1 levels. Postoperatively, biochemical cure was documented in 20 out of 24 patients. Creatinine levels (mean ± SEM) increased from 72 ± 3 to 80 ± 3 µmol/l (p = 0.0004) and concurrently, estimated GFR decreased from 99 ± 3 to 91 ± 3 ml/min (p = 0.0008). In contrast to creatinine, CysC levels decreased from 0.72 ± 0.02 to 0.68 ± 0.02 mg/l (p = 0.0008).
  
  
  CONCLUSIONS
  Our study provides strong evidence for discordant effects of GH on creatinine and CysC in patients with acromegaly undergoing transsphenoidal surgery, thus identifying another hormone that influences CysC independent of renal function.
authors.affiliation: Division of Endocrinology and Diabetes, Kantonsspital, St. Gallen, Frauenfeld, Switzerland ; Division of Endocrinology and Diabetes, Kantonsspital, St. Gallen, Frauenfeld, Switzerland.
authors.forename: Lisa
authors.initials: L
authors.lastname: Sze
authors.affiliation: Department of Neurosurgery, University Hospital, Frauenfeld, Switzerland ; Department of Neurosurgery, Clinic Hirslanden, Zurich, Frauenfeld, Switzerland.
authors.forename: René L
authors.initials: RL
authors.lastname: Bernays
authors.affiliation: Division of Endocrinology and Diabetes, Kantonsspital, St. Gallen, Frauenfeld, Switzerland.
authors.forename: Cornelia
authors.initials: C
authors.lastname: Zwimpfer
authors.affiliation: Department of Internal Medicine, Kantonsspital Frauenfeld, Frauenfeld, Switzerland.
authors.forename: Peter
authors.initials: P
authors.lastname: Wiesli
authors.affiliation: Division of Endocrinology and Diabetes, Kantonsspital, St. Gallen, Frauenfeld, Switzerland.
authors.forename: Michael
authors.initials: M
authors.lastname: Brändle
authors.affiliation: Division of Endocrinology and Diabetes, Kantonsspital, St. Gallen, Frauenfeld, Switzerland.
authors.forename: Christoph
authors.initials: C
authors.lastname: Schmid
keywords: Acromegaly; Creatinine; Cystatin C; Growth hormone; Kidney