Fibroblast growth factor-23 in patients with Graves' disease before and after antithyroid therapy: its important role in serum phosphate regulation.

Abstract

OBJECTIVE:

Hyperthyroidism is a well-described cause of hyperphosphatemia. We aimed to clarify the physiological role of fibroblast growth factor (FGF)-23 in serum phosphate homeostasis in patients with Graves' disease during the course of treatment for hyperthyroidism.

CONTEXT:

The study group comprised 56 patients (45 for a cross-sectional study and 11 for a longitudinal study) with Graves' disease. For the cross-sectional study, patients were assigned, on the basis of their serum phosphate level, to a hypophosphatemia group (n = 14), a normophosphatemia group (n = 16), or a hyperphosphatemia group (n = 15). Serum FGF-23, calcium, phosphate, PTH, and 1,25-dihydroxyvitamin D [1,25(OH)(2)D] levels were compared between the three groups. For the longitudinal study, we assessed changes in these biochemical indices before and after antithyroid treatment.

RESULTS:

In the cross-sectional study, the serum FGF-23 level was significantly higher (P < 0.05) in the hyperphosphatemia group than in the other groups (61 +/- 36 ng/liter vs. 31 +/- 22 ng/liter and 30 +/- 9 ng/liter). In the longitudinal study, serum levels of FGF-23 decreased significantly (P < 0.05) from a high of 54 +/- 12 ng/liter before treatment to 29 +/- 14 ng/liter after treatment. In contrast, the serum 1,25(OH)(2)D level increased significantly (P < 0.005) from 55 +/- 22 pmol/liter before treatment to 185 +/- 76 pmol/liter 3 months after treatment. Serum FGF-23 levels were positively correlated with serum phosphate levels (P < 0.0001) and negatively correlated with serum 1,25(OH)(2)D levels (P < 0.0001).

CONCLUSIONS:

The significant positive correlation between serum levels of phosphate and FGF-23 indicates that FGF-23 may play an important role in serum phosphate homeostasis by its up-regulation in the hyperphosphatemic condition.

• Authors: Hiroyuki Yamashita, Yuji Yamazaki, Hisashi Hasegawa, Takeyoshi Yamashita, Seiji Fukumoto, Takashi Shigematsu, Junichiro James Kazama, Masafumi Fukagawa, Shiro Noguchi
• Journal: The Journal of clinical endocrinology and metabolism (J Clin Endocrinol Metab) Vol. 90 Issue 7 Pg. 4211-5 (Jul 2005) ISSN: 0021-972X [Print] United States
• PMID: 15827108 (Publication Type: Journal Article)

Chemical References

• Antithyroid Agents
• FGF23 protein, human
• Parathyroid Hormone
• Phosphates
• Fibroblast Growth Factors
• Fibroblast Growth Factor-23
• Calcium

Topics

• Adult
• Aged
• Antithyroid Agents (therapeutic use)
• Calcium (blood)
• Cross-Sectional Studies
• Female
• Fibroblast Growth Factor-23
• Fibroblast Growth Factors (blood, physiology)
• Graves Disease (blood, drug therapy)
• Humans
• Male
• Middle Aged
• Parathyroid Hormone (blood)
• Phosphates (blood)