Funções homeostáticas da pele e homeostase fósforocálcica na deficiência congênita e isolada do GH

Abstract

Introduction: The skin performs protective functions (against microorganisms, dehydration, ultraviolet radiation and mechanical damage) and homeostatic functions (sweating and 25-hydroxyvitamin production). There is a reciprocal relationship between the skin and the GH/IGF-I axis. The skin produces both IGF-I and vitamin D, and GH and IGF-I perform various functions on the skin. Reduction in sweating and 25- hydroxyvitamin D levels are described in GH-deficient individuals (GHD), especially in the context of hypopituitarism. The parameters of calcium and phosphorus homeostasis are relatively unknown in isolated GH deficiency (IGHD). For 25 years, we studied a cohort with IGHD due to the c.57 + 1G>A mutation in the GHRH receptor gene, which live in the municipality of Itabaianinha in northeast of Brazil. These individuals have severe short stature, reduced muscle mass, but with adequate muscle and bone function, central obesity, and normal longevity. They are active performing outdoor activities with adequate sun exposure. Objectives: To evaluate the homeostatic functions of the skin, sweating and production of 25-hydroxyvitamin D and phosphoric-calcium homeostasis in individuals with Itabaianinha IGHD. Possible influencing factors on these functions such as metabolic, inflammatory profile and muscle mass will be analyzed as well. Methods: cross-sectional study with 20 DIGH individuals, 11 men, 49.4 (13.4) years old and 20 controls, 11 men, 48.9 (13.6) years old. Sweating was collected with the Macroduct® Sweat Collection System after 30 minutes of pilocarpine iontophoresis and afterwards the conductivity was measured by Sweat Check® and the chloride was measured by colorimetric method. IGF-I, insulin, PTH, 25-hydroxyvitamin D, C-reactive protein (CRP), CPK, glucose, calcium, phosphorus, alkaline phosphatase, total protein and fractions, and urinary calcium were measured. HOMA-IR was calculated. Results: DIGH individuals presented lower sweating (p = 0.012), with an increase in chloride (p = 0.019) and conductivity (p = 0.006). However, their vitamin D concentrations and the consequent phosphorus-calcium homeostasis are normal. Additionally these individuals had lower HOMA-IR (p = 0.002), translating better metabolic profile, higher CRP (p <0.0001), chronic inflammation and lower CPK (p = 0.005), lower muscle mass. Conclusion: Untreated IGHD leads to reduced sweating, but does not affect vitamin D concentrations and phosphorus-calcium homeostasis.