Session: SUN 234-256-Bone & Calcium Metabolism: Clinical Trials & Case Series
Poster Board SUN-237
Clinical Case: A 76 year-old female with stage 3 CKD, chronic pancreatitis and vit-D deficiency, was evaluated for high plasma PTH levels. Her medications included ergocalciferol 50,000 IU weekly, oral conjugated estrogen 0.625 mg daily and pancrelipase. Physical examination was unremarkable. Lab data revealed Ca: 9.1 mg/dL, albumin: 4.3 g/dL, Cr: 1.44 mg/dL, GFR: 35 L/min/1.73 m2, PTH: 452 pg/mL (nl 14-72), 25(OH)D: 29 ng/mL and 1,25(OH)D: 23 pg/mL (nl 15-75). The diagnoses of increased DBP, secondary hyperparathyroidism caused by CKD and vit-D deficiency (due to malabsorption) were made. Though not directly measured, it was suspected that her DBP was elevated due to oral estrogen therapy while the bioavailable 25(OH)D was low. As a surrogate of DBP, SHBG and CBG were measured, and were both elevated (79 nmol/L and 69 mg/L, respectively). Ergocalciferol was increased to 50,000 IU 4 times a week, which resulted in lowering PTH level to near 150 pg/mL and also an increase in 25(OH)D level to 91 ng/mL. On the latter regimen, both PTH and 25(OH)D had remained relatively unaltered for 5 months until estrogen administration route was changed from oral to transdermal. With that change, serum levels of SHBG and CBG normalized; and despite being maintained on the same dose of ergocalciferol, plasma PTH decreased to 77 pg/mL while 25(OH)D level was unchanged with stable serum calcium, phosphorus, creatinine and GFR.
Summary and conclusions: Circulating DBP level is increased by oral estrogen. 25(OH)D level in individuals taking estrogen may appear normal, even in those with true vit-D deficiency. Since measurements of DBP and free 25(OH)D are not currently available, clinical judgment on vit-D replacement therapy should be primarily based on other lab values, such as PTH, Ca, with close monitoring of the trend of 25(OH)D levels.
Nothing to Disclose: RM, BMA
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