Update on Measuring Ketones

Ketone bodies are an energy substrate produced by the liver and used during states of low carbohydrate availability, such as fasting or prolonged exercise. High ketone concentrations can be present with insulin insufficiency and are a key finding in diabetic ketoacidosis (DKA). During states of insulin deficiency, lipolysis increases and a flood of circulating free fatty acids is converted in the liver into ketone bodies-mainly beta-hydroxybutyrate and acetoacetate. During DKA, beta-hydroxybutyrate is the predominant ketone in blood. As DKA resolves, beta-hydroxybutyrate is oxidized to acetoacetate, which is the predominant ketone in the urine. Because of this lag, a urine ketone test might be increasing even as DKA is resolving. Point-of-care tests are available for self-testing of blood ketones and urine ketones through measurement of beta-hydroxybutyrate and acetoacetate and are cleared by the US Food and Drug Administration (FDA). Acetone forms through spontaneous decarboxylation of acetoacetate and can be measured in exhaled breath, but currently no device is FDA-cleared for this purpose. Recently, technology has been announced for measuring beta-hydroxybutyrate in interstitial fluid. Measurement of ketones can be helpful to assess compliance with low carbohydrate diets; assessment of acidosis associated with alcohol use, in conjunction with SGLT2 inhibitors and immune checkpoint inhibitor therapy, both of which can increase the risk of DKA; and to identify DKA due to insulin deficiency. This article reviews the challenges and shortcomings of ketone testing in diabetes treatment and summarizes emerging trends in the measurement of ketones in the blood, urine, breath, and interstitial fluid.

A Case of Hypercalcemia from PTHrP-Producing Fibromyxoid Sarcoma Responsive to Glucocorticoid Therapy

The treatment of parathyroid hormone-related protein (PTHrP)-mediated hypercalcemia of malignancy includes treating the malignancy, intravenous fluids, and anti-resorptive therapies such as zoledronic acid or denosumab. PTHrP-mediated hypercalcemia has been reported in benign conditions such as systemic lupus erythematous (SLE) and sarcoidosis and appears to be responsive to glucocorticoids. We report a case of PTHrP-induced hypercalcemia due to a malignancy-low grade fibromyxoid sarcoma-that responded to glucocorticoid treatment. This is the first report of glucocorticoids controlling PTHrP-mediated hypercalcemia of malignancy. Immunohistochemistry of the surgical pathology localized PTHrP staining to the vascular endothelial cells within the tumor. Further studies are needed to elucidate the mechanism of glucocorticoid action in the treatment of PTHrP-mediated hypercalcemia of malignancy.

PSAT208 A Case of Hypercalcemia From PTHrP-Producing Fibromyxoid Sarcoma Responsive to Glucocorticoid Therapy

Background

Parathyroid hormone-related protein (PTHrP) is a major cause of humoral hypercalcemia of malignancy. PTHrP-induced hypercalcemia can also occur in benign disorders including pneumonia, SLE, HIV, sarcoidosis, and mammary hyperplasia. Treatment for PTHrP-induced hypercalcemia includes treating the underlying disorder and general management of hypercalcemia.

Clinical Case

A 70-year-old male with a chronic left thigh mass following trauma 12 years prior diagnosed as myositis ossificans, presented with worsening pain and swelling over the mass. Evaluation revealed serum calcium 18.6 mg/dl, PTH 10 ng/L (18-90), 25(OH)D 7 ng/ml (20-50), 1,25(OH)2D 15 pg/ml (20-79), PTHrP 9.3 pmol/L (≤ 4.2), negative SPEP, UPEP, serum light chains and immunofixation, and no bony lesions. MRI showed a large heterogenous mass centered in the left adductor muscle compatible with chronic hematoma with myositis ossificans. FDG PET/CT scan showed FDG avidity and calcification of the left thigh without any other site of uptake. Combination of IV hydration, denosumab and zoledronic acid lowered his calcium to 9.5 mg/dl, but levels increased again within 10 days. Repeated treatments with zoledronic acid initially led to modest lowering of calcium to 10.5 mg/dl, but he became refractory to treatment after 6 weeks, with calcium increasing to 12.3 mg/dl.Two biopsies of the mass were performed, including an open biopsy. The pathology showed nonpolarizable crystalline material with foreign giant cell reaction, without evidence for malignancy. It was concluded therefore that the patient's PTHrP-induced hypercalcemia was secondary to an inflammatory granulomatous condition. Since it had been reported that PTHrP-induced hypercalcemia in SLE and sarcoidosis responded to glucocorticoids, we initiated treatment with methylprednisolone 24 mg daily. After 7 days, the calcium declined from 12.3 to 10.5 mg/dl and PTHrP declined to 2.5 pmol/L. When the methylprednisolone dose was reduced to 12 mg daily, calcium increased to 11.4 mg/dl and PTHrP to 5 pmol/L. Increasing the methylprednisolone briefly back to 24 mg daily, and then 20 mg daily, lowered calcium to 9.0 mg/dl, increased PTH to 74 ng/L, and normalized PTHrP to 1.3 pmol/L. As long-term management with high-dose steroids was not a tenable option, a decision was made to resect the mass. The pathological diagnosis of the surgical mass was low-grade fibromyxoid sarcoma (LGFMS). Immunohistochemical studies identified PTHrP in surrounding vasculature, suggesting possible tumor-vessel interaction.

Conclusion

PTHrP-mediated hypercalcemia is rarely seen in sarcomas and treatments include coadministration of bisphosphonates, chemotherapy and surgery. We report here the first case of PTHrP-induced hypercalcemia from LGFMS with sustained lowering of calcium and PTHrP levels with glucocorticoid treatment. Further studies are needed to elucidate the mechanism of glucocorticoids in the treatment of PTHrP-induced hypercalcemia and could include lowering levels of inflammatory cytokines that stimulate PTHrP production from tumor cells, or by directly suppressing PTHrP gene expression.

Presentation: Saturday, June 11, 2022 1:00 p.m. - 3:00 p.m.