Preferred Sample Type

Fibroblast growth factor 23 (FGF-23)

Suitable Specimen Types

  • EDTA Plasma
5 mL Whole Blood

Specimen Transport

Transport to Laboratory ASAP.

Sample Processing in Laboratory

Store frozen and transport to referral laboratory on dry ice.

Sample Preparation

Separate plasma ASAP and store frozen.

Fibroblast growth factor 23 (FGF-23)

General Information

Fibroblast growth factor 23 (FGF-23) is a recently discovered growth factor produced by osteocytes and behaving as a hormone in phosphate homeostasis.1 FGF-23 decreases phosphate reabsorption in the kidney by down-regulating the expression of sodium-phosphate co-transporters in the proximal tubule. Moreover, FGF-23 inhibits 1a-hydroxylase expression, leading to decreased hydroxylation of 25- hydroxyvitamin D to 1,25-dihydroxyvitamin D. Increased FGF-23 concentrations, due to genetic mutations, cause excessive renal phosphate excretion and inappropriately low plasma 1,25-dihydroxyvitamin D concentrations in several types of hereditary hypophosphatemic rickets. Tumour-induced osteomalacia is a syndrome consisting of hypophosphataemia, due to decreased renal tubular phosphate reabsorption, inappropriately low 1,25-dihydroxyvitamin D, myopathy and osteomalacia, caused by tumour production of FGF-23.

Patients undergoing haemodialysis often have both increased serum phosphate and FGF-23 concentrations. FGF-23 concentrations in these patients appear to be independently associated with mortality.

Taken from Heijboer et al., Ann Clin Biochem 2009; 46: 338–340

Patient Preparation

It is recommended that the patient is fasted.

Reference Range

Provided by referral laboratory.


  • EQA Scheme?: No

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The Trust Laboratories at Heartlands Hospital, Good Hope Hospital and Solihull Hospital were awarded UKAS (United Kingdom Accreditation Service) accreditation to the internationally recognised ISO 15189 standard in May 2015. For a list of accredited tests and other information please visit the test database
Tests not appearing on this scope are either under consideration or in the process of accreditation and so currently remain outside of our scope of accreditation. However, these tests have been validated to the same high standard as accredited tests and are performed by the same trained and competent staff.

For further information contact Louise Fallon, Quality Manager, 0121 424 1235