There is a high percentage of individuals with vitamin D insufficiency in Brazil, even in cities near the equator, and this percentage progressively increases with more southern latitudes.

The low-density lipoprotein receptor-related protein (Lrp)-5 regulates osteoblast proliferation and bone formation through its expression in duodenum by modifying the gut serotonin-bone endocrine axis. However, its direct role, if any, in osteoblast progenitor cells has not been studied thus far. Here, we show that mice with a Dermo1-Cre-mediated disruption of Lrp5 in osteoblast progenitor cells have normal embryonic skeletogenesis and normal skeletal growth and development postnatally. Histomorphometric analysis of 3-month-old adult mice revealed normal osteoblast numbers, bone formation rate, and bone mass in Lrp5(Dermo)(-/-) mice. In addition, analysis of two osteoporosis pseudoglioma (OPPG) patients revealed a three- to fivefold increase in their serum serotonin levels compared to age-matched controls. These results rule out a direct function of Lrp5 in osteoblast progenitor cells and add further support to the notion that dysregulation of serotonin synthesis is involved in bone mass abnormalities observed in OPPG patients.

Osteoporosis Pseudoglioma (OPPG) is characterized by severe juvenile-onset osteoporosis and ocular abnormalities. It is caused by one of several inactivating mutations in LRP5, a gene importantly involved in bone formation. The objective of this study was to evaluate the efficacy of teriparatide in a young man with OPPG. The subject of this case report is a 19-year-old man with congenital blindness and low trauma fractures because of OPPG. A 2-year course of teriparatide, 20 mg/day, was initiated after a 6-year course of intravenous pamidronate infusions, the latter 3 years of which had minimal effects on bone mineral density (BMD). Measurements in serum were made of C-terminal telopeptide of type I collagen (CTX), N-terminal propeptide of type I collagen (P1NP), total and ionized calcium, phosphate, uric acid, complete blood count, and renal and liver function tests. Urinary calcium/creatinine ratio was determined. BMD was measured by DXA yearly. BMD increased by 9.7% in lumbar spine and 10.2% in right femur hip. CTX rose early, peaking in month 3, followed by an increase in P1NP, peaking in month 9. Both indices returned to baseline by month 24. The increase in CTX followed by P1NP is an unusual time course when teriparatide is used to treat osteoporosis but may be typical of low bone turnover states. There were no adverse events. In a patient with OPPG, teriparatide markedly increased BMD in the lumbar spine and femur hip. ß

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SUMMARYOsteoporosis is a disease characterized by low bone mass associated with the deterioration of microarchitecture, due to an imbalance either in high bone resorption or low bone formation or in both, leading to a high risk of fractures. Bisphosphonates are medications which reduce the ability of osteoclasts to induce bone resorption and consequently improve the balance between resorption and formation. There are bisphosphonates approved for the prevention and treatment of osteoporosis. Administration can be oral (daily, weekly or monthly) or intravenous (quarterly or yearly). These medications are well tolerated and with the correct instructions of administration have a good safety profile. Serious side effects, such as, osteonecrosis of jaw is very rare. Bisphosphonates are the most prescribed medication for the treatment of osteoporosis. Arq Bras Endocrinol Metab. 2010;54(2):206-12 Keywords Bisphosphonates; mechanism of action; osteoporosis treatment; side effects SUMÁRIO Osteoporose é uma doença caracterizada por baixa massa óssea associada à deterioração da microarquitetura devido ao desbalanço pela alta reabsorção, baixa formação ou ambas, levando a um alto risco de fraturas. Bisfosfonatos são medicamentos que reduzem a capacidade de os osteoclastos induzirem a reabsorção óssea e, consequentemente, melhorar o balanço entre reabsorção e formação. Há bisfosfonatos aprovados para prevenção e tratamento da osteoporose. A administração pode ser via oral (diária, semanal ou mensal) ou intravenosa (trimestral ou anual). Essas medicações são bem toleradas e, seguindo as recomendações adequadas, apresentam alto grau de perfil de segurança. Efeitos colaterais sérios, como osteonecrose de mandíbula, são raros. Bisfosfonatos são as medicações mais prescritas para o tratamento da osteoporose. Arq Bras Endocrinol Metab. 2010;54(2):206-12 Descritores Bisfosfonatos; mecanismo de ação; tratamento da osteoporose; efeitos colaterais