Pathology Handbook

Calcium Excretion

Synonyms

-

Clinical Indications

Exclusion of Familial Benign Hypercalcaemia (FBH) in patients with suspected primary hyperthyroidism (PHPTH).  FBH is a condition which can be mistaken for PHPTH because of some common clinical and biochemical features. In contrast with PHPTH, treatment of FBH by parathyroidectomy almost never results in normalisation of serum calcium and surgery is therefore contra-indicated.

Request Form

Request on ICE

Availability

On request.

Specific Criteria

Patient should have been shown to have  hypercalcaemia. 

Patient Preparation

Patient must fast overnight (10 hours)

Turnaround Time

Same day

Specimen

Fasting serum and 2nd void fasting urine.

PTH should be measured at the same time

Volume

2 ml serum and 5ml urine

Container

Yellow top (SST) tube (serum), white capped universal container (urine) and Lemon top (Biochemistry SST) sample (for PTH)

Urine bottle white top 

Vacutainer lemon top

 Vacutainer gold top

Causes for Rejection

Unlabelled samples. Patient not fasting.

Reference Range

See laboratory report

Urine excretion is low in FBH. At a cut-off of 22 m mol/l glomerular filtrate, sensitivity for the diagnosis of FBH is 95% and specificity 92%.