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      Avaliação plasmática de igf-1 no prolactinoma Translated title: IGF-1 plasma levels evaluation in prolactinoma

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          Prolactinomas são os tumores hipofisários mais comuns, podendo co-secretar GH (hormônio do crescimento). IGF-1 (fator de crescimento insulina-símile-1) é o principal responsável pelas ações do GH e parâmetro diagnóstico de acromegalia. Objetivando determinar por uma dosagem de IGF-1, na avaliação inicial de pacientes com prolactinoma, ocorrência de tumores mistos [GH e prolactina (PRL)], estudamos 7 homens e 27 mulheres, entre 19 e 72 anos, confrontando-os aos resultados de GH basal e durante teste oral de tolerância à glicose, quando GH basal >0,4 ng/mL ou níveis de IGF-1 alterados. A proporção de pacientes com GH >0,4 ng/mL e IGF-1 elevada foi alta; mas, após administração de 75g de glicose por via oral, nenhum paciente foi diagnosticado como acromegálico. Sugerimos, porém que a dosagem de IGF-1 seja realizada pelo risco de co-secreção de GH nos prolactinomas. Atenção especial para pacientes que apresentem significativa diminuição dos níveis de PRL, sem correspondente regressão do tamanho do adenoma.

          Translated abstract

          Prolactinomas are the most frequent pituitary tumors and may co-secrete GH (growth hormone). IGF-1 (insulin-like growth factor-1) is the main responsible for GH actions and a parameter for the diagnosis of acromegaly. With the objective of identifying through a IGF-1 levels analysis, in the initial evaluation of prolactinoma patients, the existence of mixed tumors [GH and prolactin (PRL)], we studied 7 men and 27 women, aged between 19 and 72 years, confronting them with the results of basal and glucose stimulated (glucose tolerance test - GTT) GH levels, indicated when GH >0.4 ng/mL or IGF-1 levels were elevated. The prevalence of patients with GH >0.4 ng/mL and elevated IGF-1 was higher than expected; however, after GTT, no patient fulfilled the diagnostic criteria for acromegaly. However, we suggest that, they should be submitted to IGF-1 evaluation, due to the risk of GH co-secretion in prolactinomas. Special attention should be paid to those who present a significant decrease of PRL levels without concomitant tumor size reduction.

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          Most cited references 30

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          Gender and age influence the relationship between serum GH and IGF-I in patients with acromegaly.

          In patients with acromegaly serum IGF-I is increasingly used as a marker of disease activity. As a result, the relationship between serum GH and IGF-I is of profound interest. Healthy females secrete three times more GH than males but have broadly similar serum IGF-I levels, and women with GH deficiency require 30-50% more exogenous GH to maintain the same serum IGF-I as GH-deficient men. In a selected cohort of patients with active acromegaly, studied off medical therapy using a single fasting serum GH and IGF-I measurement, we have reported previously that, for a given GH level, women have significantly lower circulating IGF-I. To evaluate the influence of age and gender on the relationship between serum GH and IGF-I in an unselected cohort of patients with acromegaly independent of disease control and medical therapy. Sixty (34 male) unselected patients with acromegaly (median age 51 years (range 24-81 years) attending a colonoscopy screening programme were studied. Forty-five had previously received pituitary radiotherapy. Patients had varying degrees of disease control and received medical therapy where appropriate. Mean serum GH was calculated from an eight-point day profile (n = 45) and values obtained during a 75-g oral glucose tolerance test (n = 15). Serum IGF-I, IGFBP-3 and acid-labile subunit were measured and the dependency of these factors on covariates such as log10 mean serum GH, sex, age and prior radiotherapy was assessed using regression techniques. The median calculated GH value was 4.7 mU/l (range 1-104). A significant linear association was observed between serum IGF-I and log10 mean serum GH for the cohort (R = 0.5, P < 0.0001). After simultaneous adjustment of the above covariates a significant difference in the relationship between mean serum GH and IGF-I was observed for males and females. On average, women had serum IGF-I levels 11.44 nmol/l lower than men with the same mean serum GH (P = 0.03, 95% CI 1.33-21.4 nmol/l). Age significantly influenced the relationship and for a given serum GH, IGF-I was estimated to fall by 0.37 nmol/l per year (P = 0.04, 95% CI 0.015-0.72). In keeping with previous observations of relative GH resistance in normal and GH-deficient females we have observed lower serum IGF-I levels for equivalent mean serum GH levels in females patients with acromegaly. This gender-dependent difference is independent of disease activity and the use of concomitant medical therapy. Additionally, we have demonstrated that for a given serum GH level, age significantly influences IGF-I concentrations in patients with acromegaly. These data have important implications for the use of serum IGF-I and GH as markers of disease activity in acromegaly.
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            Commercial assays available for insulin-like growth factor I and their use in diagnosing growth hormone deficiency.

             D Clemmons (2000)
            Radioimmunoassays of insulin-like growth factor I (IGF-I) are commonly used for screening adults and children for growth hormone (GH) deficiency or excess. There are, however, many problems with such assays. Attempts to resolve these problems have focused on methods of separating IGF-I from its binding proteins, and on reducing inter- and intra-assay variability. In particular, the collection of sufficient high-quality normative data is a major difficulty in many laboratories. Clinical evaluation of assays is also problematic. IGF-I levels vary with age after puberty, and this is complicated by the maintenance of IGF-binding protein 3 levels by IGF-II. Generally, studies have shown that IGF-I is sensitive and specific for the diagnosis of acromegaly, but screening for GH deficiency (GHD) is less precise. The most commonly used commercial assays are immunoradiometric (IRMA) sandwich assays, using antibodies specific to IGF-I. IRMA assays are quick and accurate, and the two-site antibody reactivity produces a high degree of specificity. Additional techniques such as acid-ethanol extraction or saturation with IGF-II can improve reliability. More recently, the introduction of chemiluminescence has provided enhanced speed and sensitivity. The clinical use of these assays has provided a wealth of information regarding the diagnosis of GHD, and it may be possible to reduce the number of patients who require provocative GH testing. IGF-I assays are also of great use in monitoring GH replacement therapy. Despite the problems, IGF-I measurement is currently the best indirect method available for screening and monitoring patients with GHD. Copyright 2001 S. Karger AG, Basel
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              Disorders of Prolaction Secretion


                Author and article information

                Role: ND
                Role: ND
                Role: ND
                Role: ND
                Role: ND
                Role: ND
                Arquivos de Neuro-Psiquiatria
                Arq. Neuro-Psiquiatr.
                Academia Brasileira de Neurologia - ABNEURO (São Paulo )
                September 2006
                : 64
                : 3b
                : 849-854
                [1 ] Universidade Federal do Rio de Janeiro Brazil
                [2 ] Universidade Federal do Rio de Janeiro Brazil
                [3 ] Universidade Federal do Rio de Janeiro Brazil
                [4 ] Universidade Federal do Rio de Janeiro Brazil
                [5 ] Universidade Federal do Rio de Janeiro Brazil
                Product Information: website


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