A brown tumor after biliopancreatic diversion for severe obesity

Comparison of calcifediol with vitamin D for prevention or cure of vitamin D deficiency

Vitamin D deficiency remains prevalent, with about 7% of the world's population living with severe vitamin D deficiency and about one third with mild deficiency. We compare the relative merits of calcifediol or 25-hydroxyvitamin D (25OHD) compared to vitamin D itself for supplementation as to prevent or cure vitamin D deficiency. The intestinal absorption of calcifediol is nearly 100% and thus higher than that of vitamin D itself. Moreover, calcifediol is absorbed by the intestinal cells and transported through the portal vein and thus immediately accessible to the circulation, while vitamin D is transported with chylomicrons through the lymph system. Therefore, in case of fat malabsorption or after bariatric surgery, calcifediol is much better absorbed in comparison with vitamin D itself. Serum 25OHD increases linearly with increasing doses of calcifediol, whereas serum 25OHD reaches a plateau when higher oral doses of vitamin D are used. Calcifediol, on a weight basis, is about 3 times more potent than vitamin D in subjects with mild vitamin D deficiency. This potency is even 6-8 times higher than vitamin D when baseline serum 25OHD is higher or when large doses are compared. In conclusion, calcifediol is an alternative option to correct vitamin D deficiency and may even be the preferred strategy in case of intestinal fat malabsorption, after bariatric surgery or in case of other conditions with suspected impaired 25-hydroxylase activity in the liver.

Vitamin D alteration associated with obesity and bariatric surgery

Obesity and severe obesity constitute growing serious health problems reaching epidemic proportion in most countries. Interactions and relationships between obesity and bone tissue and its metabolism are complex but are more and more studied and recognized. Obesity is associated with an altered hormonal profile including particularly bone-regulating hormones like vitamin D. Bariatric surgery procedures, thanks to their effectiveness to achieve therapeutic endpoints for comorbidities associated with obesity, have had an increasing success. However, these surgeries by producing mechanical restriction and or malabsorption syndrome lead to nutritional deficiencies including vitamin D. In this review, we aim to (1) discuss the nutritional deficiency of vitamin D in the obese, (2) to summarize the different surgical options in bariatric surgery and to present the evidence concerning these procedures and their associated profile in vitamin D post-operative insufficiency, (3) to present the different recommendations in clinical practice to prevent or treat vitamin D deficiencies or insufficiencies in patients treated by bariatric surgery and finally to introduce emerging assumptions on the relationship between vitamin D, microbiota composition and circulating bile acids. Impact statement Obesity and severe obesity constitute growing serious health problems reaching epidemic proportion in most countries with a prevalence increasing from 6.4 in 1975 to 14.9% in 2014. This present review summarizes currently available data on vitamin D deficiencies in the obese population before and after bariatric surgery. The important evidence emerging from our evaluation confirms that obese patients are at risk of multiple nutritional deficiencies, especially vitamin D deficiency, before bariatric surgery. Our survey confirms that the precise role of the gut microbiome and its associated changes on the vitamin D metabolism after the different bariatric surgery procedures has not yet been studied. Furthermore, whether differences in the microbiota may alter the therapeutic responses to vitamin D is not known.

Brown tumours of the tibia and second metacarpal bone in a woman with severe vitamin D deficiency

Brown tumours caused by vitamin D deficiency are rare. Most cases are caused by primary hyperparathyroidism, and are rarely caused by secondary hyperparathyroidism in cases of renal failure. We present a case of Brown tumours of the tibia and second metacarpal bone in a 50-year-old woman who had a low dietary intake of vitamin D and had worn a veil for most of her adult life. The Brown tumours were caused by vitamin D deficiency and secondary hyperparathyroidism. The patient improved on treatment with vitamin D3 and calcium supplements. This is a rare case and the first, to our knowledge, with a Brown tumour of the tibia caused by vitamin D deficiency due to decreased dietary intake and decreased exposure to sunlight. The course of treatment and investigations of the patient are described.

Vitamin D signaling in calcium and bone homeostasis: a delicate balance

Loss-of-function mutations in genes involved in the vitamin D/vitamin D receptor system have clearly evidenced its critical role for mineral and skeletal homeostasis. Adequate levels of 1,25-dihydroxyvitamin D [1,25(OH)2D], the active form of vitamin D are therefore required and depend on sufficient sunlight exposure or dietary intake. Intestinal calcium absorption is a primary target of 1,25(OH)2D action and this pathway indirectly promotes calcium incorporation in bone. Severe vitamin D deficiency may thus decrease bone quality and leads to osteomalacia, whereas less severe deficiency increases the risk of osteoporosis and bone fractures. On the other hand, high vitamin D levels together with low dietary calcium intake will increase bone resorption and decrease bone mineralization in order to maintain normal serum calcium levels. Appropriate dietary calcium intake and sufficient serum vitamin D levels are thus important for skeletal health. Dosing of calcium and vitamin D supplements is still debated and requires further investigation.

Bone metabolism after bariatric surgery

Bariatric surgery is a popular and effective treatment for severe obesity but may have negative effects on the skeleton. This review summarizes changes in bone density and bone metabolism from animal and clinical studies of bariatric surgery, with specific attention to Roux-en-Y gastric bypass (RYGB), adjustable gastric banding (AGB), and sleeve gastrectomy (SG). Skeletal imaging artifacts from obesity and weight loss are also considered. Despite challenges in bone density imaging, the preponderance of evidence suggests that bariatric surgery procedures have negative skeletal effects that persist beyond the first year of surgery, and that these effects vary by surgical type. The long-term clinical implications and current clinical recommendations are presented. Further study is required to determine mechanisms of bone loss after bariatric surgery. Although early studies focused on calcium/vitamin D metabolism and mechanical unloading of the skeleton, it seems likely that surgically induced changes in the hormonal and metabolic profile may be responsible for the skeletal phenotypes observed after bariatric surgery.

A haemodialysis patient with back pain: brown tumour as a cause of spinal cord compression under cinacalcet therapy

A 43-year-old haemodialysis patient was admitted to hospital because of paroxysmal pain in the upper abdominal region radiating to the back. Laboratory tests showed severe hyperparathyroidism [intact parathyroid hormone (iPTH) 69 pmol/L; reference range: 1.3-6.8 pmol/L], hypercalcaemia (2.79 mmol/L), hyperphosphataemia (1.6 mmol/L) and elevated serum total alkaline phosphatase (200 U/L). After developing a disturbed sensation and paraesthesia in both feet, epidural compression of the spinal cord was suspected. Magnetic resonance imaging showed a tumour that severely compressed the myelum of the thoracic spine. Histological investigation revealed a brown tumour or osteoclastoma, an erosive bony lesion caused by increased osteoclastic activity and peritrabecular fibrosis. A brown tumour is a benign tumour that is a rare complication of severe renal hyperparathyroidism. The brown tumour developed despite a 1-year treatment of the patient with cinacalcet, which, however, did not result in a major decrease in serum iPTH concentration (from 110 to 69 pmol/L: 37% reduction). Urgent decompressive neurosurgery and subtotal parathyroidectomy resulted in a complete recovery.