Discordant Calcium and Parathyroid Hormone with Presumed Epileptic Seizures

A 33-year-old woman presented for the first time at the age of 9 years with recurrent seizures and was subsequently treated for epilepsy for 2 years. At 11 years of age, it was noted that the patient had hypocalcemia with an increased parathyroid hormone (PTH)4 measured with use of an intact PTH assay. Serum calcium was 5.73 mg/dL [1.43 mmol/L; reference interval (RI) 8.82–10.42 mg/dL (2.2–2.6 mmol/L)]; serum phosphate was 10.42 mg/dL [3.36 mmol/L; RI 1.86–4.34 mg/dL (0.6–1.4 mmol/L)]; and PTH was 319.68 pg/mL [33.9 pmol/L; RI 8.49–68.84 pg/mL (0.9–7.3 mmol/L)]. Vitamin D (Total 25-OH; 25-OH D2 and D3) concentrations, magnesium concentrations, liver and renal function tests were all normal. No other endocrine abnormalities such as thyroid or gonadotropin resistance were detected. The patient also was of short stature and was overweight. However, she became overweight after the age of 13 years (body mass index at 13 years was 22.8 kg/m2), and the short stature was not significant, as she was at the lower end of the RI for height at 1.55 m. There was no cognitive impairment. Positive Chvostek sign was observed but not Trousseau sign.The patient was placed on active vitamin D (alfacalcidol) and calcium supplements. The patient was followed up for 13 years; selected laboratory results are presented in Table 1. Although the patient was managed on calcium supplements and active vitamin D and followed up at a tertiary endocrine clinic, serum phosphate concentrations remained persistently high (Table 1). This was attributed to intermittent noncompliance and unavailability of active vitamin D. The patient had also been prescribed calcium carbonate as a phosphate binder.View this table:Table 1. Trends of calcium, phosphate, and parathyroid hormone concentrations over 13 years of follow-up.a QUESTIONS TO CONSIDER1. What are the causes of hypocalcemia with an increased PTH concentration?2. What is the explanation for …