Slideshow
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Parathyroid scan
Figure 1. Parathyroid scan of the patient shows focal increased activity posterior to the lower pole of the right thyroid lobe.
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Parathyroid scan
Figure 1. Parathyroid scan of the patient shows focal increased activity posterior to the lower pole of the right thyroid lobe.
This is a case involving a 64-year-old woman with end-stage renal disease (ESRD) due to lupus nephritis who has been on hemodialysis for 7 years. She also has dementia, hypertension, obstructive sleep apnea on CPAP, and stage 1 non-small cell lung cancer post wedge resection. Over the past 12 months, her secondary hyperparathyroidism (SHPT) has become increasingly difficult to control. Intact PTH (iPTH) was persistently over 1000 pg/mL (normal range 16-80 pg/mL). The highest iPTH value was 2678 pg/mL. Serum calcium ranged from 8.2 to 10.1 mg/dL. Serum phosphorus ranged from 4.9 to 7.3 mg/dL. Alkaline phosphatase increased from 222 to 551 U/L (normal range 35-104 U/L). The woman lives with her daughter, who is also her caregiver and does most of the cooking. The patient does not pay attention to dietary phosphorus intake and she snacks on foods readily available at her residence. Due to dementia, she often forgets her medications, including cinacelcet and phosphorus binders such as sucroferric oxyhydroxide and sevelamer. The renal team met with the patient and her daughter and provided extensive counseling on renal diet and medication compliance. After that, the patient’s daughter took up the task of managing the patient’s medications and reported excellent compliance with medications and low phosphorus renal diet. The cinacalcet dose was gradually increased to 90 mg twice a day. Calcitriol was continued at 0.25 mcg 3 times a week during HD sessions. However, the patient’s iPTH remained elevated above 1500 pg/mL.
The patient’s most recent lab results showed a serum calcium level of 10.2 mg/dL, phosphorus level of 6.4 mg/dL, iPTH level of 2257 pg/mL, and alkaline phosphatase level of 551 U/L (normal range 35-104 U/L).
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This case was prepared by Yongen Chang, MD, PhD, Assistant Clinical Professor, Division of Nephrology and Hypertension, University of California-Irvine.
References
Answer: A
Hyperparathyroidism and metabolic bone disease is very common among patients with advanced chronic kidney disease (CKD) or ESRD. SHPT develops in CKD due to a combination of vitamin D deficiency, hypocalcemia, and hyperphosphatemia. Uncontrolled hyperparathyroidism leads to hyperphosphatemia, tissue or vascular calcification, and worsened osteodystrophy. KDIGO 2017 guidelines recommend maintaining PTH levels within 2 to 9 times of the upper normal limit. Treatment of SHPT and metabolic bone disease in CKD includes a combination of active vitamin D therapy such as calcitriol and calcimemetics such as cinacalcet. Controlling hyperphosphatemia with diet and meal-time phosphorus binders to reduce dietary phosphorus intake is also an integral part of the management. However, when PTH levels persist over 800 pg/mL for more than 6 months, despite exhaustive medical interventions, monoclonal proliferation and nodular tissue hyperplasia of parathyroid glands is likely present.1
Furthermore, there is decreased expression of vitamin D and calcium-sensing receptors. Thus, dose escalation of calcimimetics and active vitamin D may not be effective. Instead, surgical parathyroidectomy should be considered, especially if there is persistent hypercalcemia and/or hyperphosphatemia. In fact, parathyroidectomy is required in approximately 15% of patients after 10 years and in 38% of patients after 20 years of renal replacement therapy.2 Parathyroidectomy is associated with improved survival by 15%-57% in large observational studies of dialysis patients.1
This patient has had persistently elevated iPTH and hyperphosphatemia despite maximal medical treatment. She can benefit from a more strict diet and increased dose of phosphorus binders to reduce hyperphosphotemia. However, at this point, she likely has developed irreversible nodular hyperplasia. A parathyroid scan is indicated to confirm this. Once a parathyroid scan confirms localized hyperactivity, subtotal or total parathyroidectomy is indicated. Doubling the dose of calcitriol or changing to another form of active vitamin D is not appropriate since the patient is already borderline hypercalcemic and her serum phosphorus has been elevated. Increasing the dose of active vitamin D will worsen hypercalcemia and hyperphosphotemia, thereby increasing the risk of vascular calcification and calciphylaxis. The maximal dose of cinacalcet is 90 mg twice a day. There is no clear evidence that etelcalcetide, an IV counterpart of cinacalcet, is superior.
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