ABSTRACT Normocalcemic primary hyperparathyroidism (PHPT) is a newer phenotype of PHPT defined by elevated PTH concentrations in the setting of normal serum calcium levels. It is increasingly being diagnosed in the setting of evaluation for nephrolithiasis or metabolic bone diseases. It is important to demonstrate that PTH values remain consistently elevated and to measure ionized calcium levels to make the diagnosis. A diagnosis of normocalcemic disease is one of exclusion of secondary forms of hyperparathyroidism, including vitamin D deficiency, renal failure, medications, malabsorption, and hypercalciuria. Lack of rigorous diagnostic criteria and selection bias of the studied populations may explain the different rates of bone and renal complications. The natural history still remains unknown. Caution should be used in recommending surgery, unless clearly indicated. Here we will review the diagnostic features, epidemiology, clinical presentation, natural history, medical and surgical management of normocalcemic PHPT.

A doença óssea no hiperparatiroidismo primário grave é representada pela osteíte fibrosa cística (OFC). Dor óssea, deformidades esqueléticas e fraturas patológicas são achados comuns na OFC. A densidade mineral óssea está, usualmente, extremamente diminuída na OFC, mas é reversível após a cura cirúrgica. Os sinais e sintomas da doença óssea grave incluem dor óssea, fraturas patológicas e fraqueza muscular proximal com hiper-reflexia. O comprometimento ósseo é tipicamente caracterizado pela aparência em “sal-e-pimenta” nos ossos do crânio, erosões ósseas e reabsorção das falanges, tumores marrons e cistos. Na radiografia, observam-se desmineralização difusa e fraturas patológicas especialmente nos ossos longos das extremidades. No hiperparatiroidismo primário (HPTP) sintomático grave, as concentrações séricas de cálcio e PTH estão usualmente bem elevadas e o comprometimento renal se caracteriza pela presença de urolitíase e nefrocalcinose. Uma nova tecnologia, recentemente aprovada para uso clínico nos Estados Unidos e na Europa, torna-se provável se difundir rapidamente, pois utiliza as imagens geradas pela densitometria DXA. O escore trabecular ósseo (TBS), obtido por meio da análise do nível da textura cinza das imagens dos corpos vertebrais, fornece informações indiretas sobre a microarquitetura trabecular. Novos métodos, como a tomografia de alta resolução quantitativa periférica computadorizada (HRpqCT), têm proporcionado conhecimentos adicionais sobre os achados da microarquitetura esquelética no HPTP.

Bone disease in severe primary hyperparathyroidism (PHPT) is described classically as osteitis fibrosa cystica (OFC). Bone pain, skeletal deformities and pathological fractures are features of OFC. Bone mineral density is usually extremely low in OFC, but it is reversible after surgical cure. The signs and symptoms of severe bone disease include bone pain, pathologic fractures, proximal muscle weakness with hyperreflexia. Bone involvement is typically characterized as salt-and-pepper appearance in the skull, bone erosions and bone resorption of the phalanges, brown tumors and cysts. In the radiography, diffuse demineralization is observed, along with pathological fractures, particularly in the long bones of the extremities. In severe, symptomatic PHPT, marked elevation of the serum calcium and PTH concentrations are seen and renal involvement is manifested by nephrolithiasis and nephrocalcinosis. A new technology, recently approved for clinical use in the United States and Europe, is likely to become more widely available because it is an adaptation of the lumbar spine DXA image. Trabecular bone score (TBS) is a gray-level textural analysis that provides an indirect index of trabecular microarchitecture. Newer technologies, such as high-resolution peripheral quantitative computed tomography (HR-pQCT), have provided further understanding of the microstructural skeletal features in PHPT.