No evidence for involvement of the growth hormone/insulin-like growth factor-1 axis in psoriasis

We have examined whether alterations in the growth hormone/insulin-like growth factor-1 axis play a role in the pathogenesis of psoriasis. Serum, urine, full skin biopsies, and suction blister roofs were obtained from patients with psoriasis and from healthy controls. Serum concentrations of insulin-like growth factor-1 and insulin-like growth factor binding protein- 3 were measured by radioimmunoassay. Growth hormone-binding protein was measured by ligand-mediated immunofunctional assay. Growth hormone concentration in urine was measured by an immunometric assay, and growth hormone receptor-gene expression was measured by RNase protection assay or by quantitative reverse transcriptase polymerase chain reaction in total RNA isolated from epidermal suction blister roofs. Serum concentrations of insulin-like growth factor-1 (249 ±12 μg per liter, mean ± SEM, n = 42, and 277 ± 21 μg per liter, n = 9, for psoriatic patients and controls, respectively), insulin-like growth factor binding protein-3 (3.1 ± 0.08 mg per liter, n = 42, and 3.3 ± 0.22 mg per liter, n = 9), growth hormone- binding protein (344 ± 65 pmol per liter, n = 10, and 311 ± 83 pmol per liter, n = 9), urinary growth hormone excretion during 24 h (12.8 ± 2.7 μIU per 24 h, n = 12, and 12.3 ± 1.6 μIU per 24 h, n = 9), and epidermal growth hormone receptor gene expression [32 ± 12 X 10³ mRNA transcripts per μg total RNA (involved skin), n = 11, and 47 ± 14 X 10³ mRNA transcripts per μg total RNA, n = 9] were similar in patients and controls. For insulin- like growth factor-1 and insulin-like growth factor binding protein-3 the values in psoriatic patients were also similar to those in larger control groups, n = 195 and n = 400, respectively. In addition, we found no evidence of local expression of growth hormone or prolactin in full skin punch biopsies from psoriatic involved skin by reverse transcriptase polymerase chain reaction. In conclusion, our results suggest that alterations in the growth hormone/insulin-like growth factor-1 axis do not play a major role in the pathogenesis of psoriasis.