Paratireóides: estrutura, funções e patologia / Parathyroid glands: structure, functions and pathology

Os autores tecem considerações sobre a estrutura e funções normais das glândulas paratireóides como introdução à patologia e as repercussões clinico - patológicas tanto do excesso como da redução do paratormônio. Maior ênfase é dedicada ao hiperparatireoidismo primário quanto às causas, a fisiopatologia das alterações, os aspectos anatomopatológicos macro e microscópicos das lesões e sua patogenia, na "Osteite fibrocistica" ou "doença de von Recklinghausen dos ossos" com a correlação aos aspectos radiográficos. Apresentam caso de paciente, cuja história clinica demonstra as dificuldades encontradas para o diagnóstico da doença. Referem-se ainda às alterações e patogenia das formas de hiperparatireoidismo secundário e terciário e ao hipoparatireoidismo.

The authors present a summary on the normal anatomy and function of the parathyroid glands as well as a brief review of clinical and pathological repercussions of higher and lower parathyroid hormone production. The emphasis is given on the causes, physiopathology, anatomy, macroscopy and microscopy of the lesions and their role in the genesis of fibrocystic osteitis, also known as Von Recklinhausen disease of the bones. Radiological correlation is also given. The authors show the challenges for the diagnosis in the same cases. We also write about secondary and tertiary hyperparathyroidism, as well as hypoparathyroidism.

Extracellular calcium-sensing receptor: structural and functional features and association with diseases

The recently cloned extracellular calcium-sensing receptor (CaR) is a G protein-coupled receptor that plays an essential role in the regulation of extracellular calcium homeostasis. This receptor is expressed in all tissues related to this control (parathyroid glands, thyroid C-cells, kidneys, intestine and bones) and also in tissues with apparently no role in the maintenance of extracellular calcium levels, such as brain, skin and pancreas. The CaR amino acid sequence is compatible with three major domains: a long and hydrophilic aminoterminal extracellular domain, where most of the activating and inactivating mutations described to date are located and where the dimerization process occurs, and the agonist-binding site is located, a hydrophobic transmembrane domain involved in the signal transduction mechanism from the extracellular domain to its respective G protein, and a carboxyterminal intracellular tail, with a well-established role for cell surface CaR expression and for signal transduction. CaR cloning was immediately followed by the association of genetic human diseases with inactivating and activating CaR mutations: familial hypocalciuric hypercalcemia and neonatal severe hyperparathyroidism are caused by CaR-inactivating mutations, whereas autosomal dominant hypoparathyroidism is secondary to CaR-activating mutations. Finally, we will comment on the development of drugs that modulate CaR function by either activating (calcimimetic drugs) or antagonizing it (calcilytic drugs), and on their potential therapeutic implications, such as medical control of specific cases of primary and uremic hyperparathyroidism with calcimimetic drugs and a potential treatment for osteoporosis with a calcilytic drug

Pseudohipoparatiroidismo Tipo I

El pseudohipoparatiroidismo es una entidad infrecuente y heterogénea causada por la pérdida heterocigótica de aproximadamente el 50 por ciento de la proteína Gs alfa, caracterizada por losvalores séricos de calcio bajos, grados de fosfatemia variable elevada y resistencia variable de la PTH, con hallazgos clínicos dismórficos y en algunos casos (tipo I) asociado a retardo mental. La alteración descrita es el resultado de la disfunción de la proteína Gs alfa miembro de la superfamilia de proteínas heterotriméricas transductoras de señales intracelulares estimuladoras de la adenil ciclasa intracelular. Se revisan dos casos con el tipo pseudohipo-hiperparatiroidismo y uno de tipo I.

Estudio de la función de las paratiroides mediante la prueba del EDTA postiroidectomía subtotal / Study of the function of the parathyroid glands through EDTA test after subtotal thyroidectomy

Se emplea la prueba del EDTA para explorar la capacidad funcional de las paratiroides, en 12 pacientes que previamente habían sido tratados quirúrgicamente por bocio tóxico difuso. Se informa que las calcemias a las 2 h y a las 4 h de haber comenzado la prueba, mostraron valores inferiores al grupo control y la diferencia fue estadísticamente significativa (p < 0,05). Se señala que el 58% de los pacientes estudiados presentó un hipoparatiroidismo latente o frustre

Hipoparatiroidismo latente: las manifestaciones clínicas / Latent hypoparathyroidism: clinical manifestations

La función de las glandulas paratiroides fue estudiada en 27 pacientes con bocio tóxico difuso, que previamente habían sido tratados con cirugía p 131I. Posteriormente, una vez identificado el tipo de respuesta, los pacientes fueron clasificados en dos grupos: 1. Respuesta normal y 2. Respuesta anormal. Se contrastaron los síntomas y signos clínicos de ambos grupos, sólo la astenia presentó una diferencia con valor estadístico en el grupo con respuesta anormal (hipoparatiroidismo "latente") (p < 0,025)