M. Muñoz-Torres

Identification of Metabolic Bone Disease in Patients with Endogenous Hyperthyroidism: Role of Biological Markers of Bone Turnover

Abstract. Active hyperthyroidism is associated with reduced bone mass. Nevertheless, not all patients show the same risk for developing osteoporosis. Our aim was to analyze some clinical and biochemical potential predictors of low bone mass in hyperthyroid patients. We studied 127 consecutive hyperthyroid patients (110 females, 17 males; aged 42 ± 16 years). Bone mineral density (BMD) was measured by dual X-ray absorptiometry (DXA) at lumbar spine (LS; L2–L4) and femoral neck (FN). Data were expressed as g/cm2 and T-score. Patients were placed into two groups based on recent WHO criteria: Group A, no osteoporosis (n = 98); and group B, lumbar or femoral osteoporosis (n = 29). Study protocol included evaluation of osteoporosis risk factors, anthropometrical variables, thyroid function, and bone turnover markers. Receiver-operating characteristic (ROC) plots for the precision of bone markers and multivariate analysis for the prediction of BMD and osteoporosis were performed. Group B showed greater age and proportion of menopausal females; lower weight, height, and calcium intake; longer duration of menopause; and greater levels of total and bone alkaline phosphatase and of urine hydroxyproline. No differences in thyroid function, osteocalcin, tartrate-resistant acid phosphatase, and type I collagen C-telopeptide (ICTP) were found. The best predictive model accounted for 46% and 62% of the variability of lumbar and femoral BMD respectively and correctly classified 89% of the osteoporotic hyperthyroid patients. No significant difference in ROC plots was observed. It is concluded that hyperthyroid patients with lumbar or femoral osteoporosis show a typical clinical and biochemical profile illustrating that the relationship between BMD and bone markers is better in high turnover states. Classical bone turnover markers show high performance in the evaluation of hyperthyroid bone disease.

Avances en el conocimiento de la biología del osteoclasto: el sistema osteoprotegerina-ligando del RANK

The differentiation and activation of osteoclasts specialized cells that degrade the bone matrix are decisively regulated by the osteoprotegerin (OPG)-RANK ligand (RANKL) paracrine system. The OPG is a soluble protein, similar to other members of the tumor necrosis factor receptor superfamily, which works as a decoy receptor of RANKL. The biologic activity of OPG counteracts the effects of RANKL by competing with the receptor activator of the nuclear factor *B (RANK); subsequently, the differentiation and activation of osteoclasts is inhibited and bone resorption reduced. The critical role of this pathway in the regulation of bone metabolism has been signalled by the finding of extreme phenotypes (osteoporosis vs. osteopetrosis) in animal models. Further studies with these factors will provide the development of drugs to treat osteoporosis and other metabolic bone diseases.La diferenciacion y activacion de los osteoclastos, celulas especializadas que degradan la matriz osea, se encuentran reguladas de forma decisiva por el sistema paracrino osteoprotegerina (OPG)-ligando del receptor activador del factor nuclear *B (RANKL). La osteoprotegerina es una proteina soluble, similar a otros miembros de la superfamilia del factor de necrosis tumoral, que actua como receptor senuelo del RANKL. Su actividad biologica contrarresta los efectos del RANKL al competir por la activacion del receptor activador del factor nuclear *B y de esta forma inhibe la diferenciacion y activacion de osteoclastos y disminuye la resorcion osea. El papel decisivo de este sistema en la regulacion del metabolismo oseo se ha demostrado por el hallazgo de fenotipos extremos (osteoporosis frente a osteopetrosis) en modelos animales. Futuros estudios sobre estos factores permitiran desarrollar farmacos para el tratamiento de la osteoporosis y otras enfermedades metabolicas oseas.

Encuesta sobre práctica clínica en el hiperparatiroidismo primario

Una reciente conferencia de consenso, promovida por los National Institutes of Health y la Endocrine Society, ha establecido un conjunto de recomendaciones para el tratamiento del hiperparatiroidismo primario en la practica clinica. Sin embargo, no se conoce los grados de conocimiento y de cumplimiento de estas recomendaciones por parte de los endocrinologos espanoles. En este articulo se revisan las recomendaciones del consenso y se presenta una encuesta elaborada por el Grupo de Trabajo de Metabolismo Mineral Oseo de la SEEN.

Varón XYY con azoospermia

Las anomalias que involucran a los cromosomas sexuales son las mas frecuentes entre el conjunto de todas las alteraciones cromosomicas. Aproximadamente 1 de cada 1.000 varones es portador de un cromosoma Y adicional, ya sea en forma pura (47,XYY) o en diversas variantes de mosaicismos. Existe una notable variabilidad en la presentacion clinica y el pronostico de cada una de las aneuploidias que comprometen a los cromosomas sexuales. En individuos con cariotipo XYY se han descrito variables caracteristicas fenotipicas y conductuales. La funcion gonadal y reproductiva de los varones XYY adultos suele ser normal y habitualmente son fertiles. Se describe el caso de un varon de 45 anos con esterilidad primaria por azoospermia con aplasia de celulas germinales en la biopsia de testiculo. El estudio citogenetico mostro un cariotipo XYY y no se evidenciaron microdelecciones de la region AZF de los cromosomas Y. Se resenan los principales aspectos del sindrome XYY y se destaca su variable presentacion clinica.