Strategies to limit renal stone formation in patients with hypoparathyroidism

Sophie Jones; Jeremy Cox

doi:10.1530/endoabs.100.WF2.2

A 60 year old female developed iatrogenic hypoparathyroidism and hypothyroidism following a total thyroidectomy, performed for a multinodular goitre, in 1981. Post-operatively, this was treated with levothyroxine 100 mg daily, alfacalcidol 2 mg daily and Adcal-D3 four tablets daily. Other past medical history included hypertension, bilateral cataract extraction and recurrent hypokalaemia with high urinary potassium losses. Hypertension was treated with candesartan 8 mg and amiloride 5 mg once daily. 35 years after first developing hypoparathyroidism, a routine surveillance CT of the renal tract identified asymptomatic 4 mm and 6 mm non-obstructing renal calculi. Following this, 2 × 24 hr urine collections demonstrated high total urine output, and urinary calcium excretion of >10 mmol/day with normal urinary citrate excretion. Urinary Calcium/Creatinine Excretion ratio was 0.039. Recurrent hypokalaemia prevented the use of indapamide or other thiazide-like diuretics to reduce urinary calcium losses.Table 1: 24hr urine collection results, concurrent blood results and medicationShe presented for routine clinical review and reported polydipsia, consuming 3-4 l/day. She denied urinary frequency, polyuria, or nocturia. There was no evidence of hypokaleamia, hypercalcaemia or diabetes. On alfacalcidol 2 mg/day, and Ad-cal D3 400 IU/750 mg 4 tabs/day, blood tests showed: cCa 2.48 mmol/l, Phos 1.62 mmol/l, eGFR 84 ml/min/1.73 m2, Na 139 mmol/l, K 4.5 mmol/l, PTH <0.3 pg/ml, TSH 0.02 IU/l, fT3 4.7 pmol/l, fT4 18.8 pmol/l. This precipitated a discussion regarding target serum calcium levels when treating hypoparathyroidism, especially in a patient with a history of renal calculi. Strategies for reducing the renal fractional excretion of calcium include both reducing calcium delivery to the glomerulus (by limiting serum calcium concentration) and promoting tubular calcium reabsorption using thiazide-diuretics. Furthermore, these patients are at high risk of nephrogenic diabetes insipidus (vasopressin resistance) due to nephrocalcinosis and the reporting of polyuria necessitates careful assessment.

Table 1. 24 hr urine collection results, concurrent blood results and medication
Urine Collection 1: 24hrs Total Volume: 3666 mls [<3l]			Urine Collection 2: 24hrs Total Volume: 4056mls
Na⁺	47 mmol/l	172 mmol/day	Creatinine	2.0 mmol/l	8.1 mmol/day (7-13)
K⁺	13.1 mmol/l	48 mmol/day	Ca²⁺	2.47 mmol/l	10.01 mmol/day (2.5-7.5)
			Phosphate	3.82 mmol/l	15.62 mmol/day (13-42)
			Mg²⁺	1.05 mmol/l	4.3 mmol/day (2.4-6.5)
			Citrate		1.64 mmol/day (>1)
Concurrent Blood Tests			Medication
Na⁺	139 mmol/l (133-146)		Candesartan 8 mg OD
K⁺	4.2 mmol/l (3.5-5.3)		Amiloride 5 mg OD
Cr	72 mmol/l (55-110)		Alfacacidol 2 mg OD
cCa²⁺	2.28 mmol/l (2.2-2.6)		Adcal D3 400 u/750 mg 4 daily
Phosphate	1.16 mmol/l (0.8-1.5)
Urinary Ca/Cr excretion ratio: 0.039

Endocrine Abstracts

WF2.2