Fibroblast growth factor 23 is elevated in patients with euthyroid Graves

Chia-Hung Lin; Shyang-Rong Shih; Keh-Sung Tsai

doi:10.1530/endoabs.56.P1030

Background: Graves’ disease (GD) is associated with accelerated bone turnover and elevated fibroblast growth factor 23 (FGF23). FGF23 is involved in the mineral homeostasis, especially the regulation of serum phosphate. Literatures showed that FGF23 decreased along with treatment of GD. It remains unclear whether FGF23 becomes normal after euthyroid status achieved.

Methods: A total of 64 patients with euthyroid GD and 64 healthy control subjects were enrolled. Endocrine profiles including thyroid autoimmune profiles, FGF23 and bone turnover markers were obtained and compared between two groups and within each group.

Results: Euthyroid GD patients have significantly higher FGF23 and phosphate, and lower 25-hydroxyvitamin D (25OH-VitD) and intact parathyroid hormone (iPTH) levels than the control group. FGF23 was significantly and negatively correlated with phosphate level after adjusted for age, gender, calcium, iPTH and 25OH-VitD in euthyroid GD group.

**Table 1** Clinical characteristics of study subjects.
	Euthyroid GD	Control	P
N	64	64
Age (years)	47.6±10.9	48.0±10.8	0.8523
Gender (female: male)	51:13	50:14	0.828
Corrected calcium (mg/dl)	9.12±0.48	9.23±0.29	0.1874
Phosphate (mg/dl)	4.24±0.78	3.84±0.51	0.0044
25-OH Vitamin D (ng/dl)	16.40±5.52	23.20±5.24	<0.0001
iPTH (pg/ml)	15.39±8.82	25.79±11.25	<0.0001
FGF23 (pg/ml)	59.10 (45.18–95.09)	46.00 (27.21–60.55)	0.0003
PINP (ng/ml)*	49.70±19.65	54.12±20.65	0.5293
CTX (ng/ml)*	0.21±0.12	0.23±0.09	0.5995
*Data of PINP and CTX were analyzed in 23 euthyroid GD subjects and 13 control subjects.

**Table 2** The relationship of FGF23 and phosphorous in linear regression model, using FGF23 as the dependent variable and serum phosphate as the independent variable.
	Euthyroid Graves’ disease group	Control group
Crude
Regression coefficient	−31.6	8.5
p value	0.015	0.260
Adjusted for age, gender, calcium, parathyroid hormone and 25-OH vitamin D
Regression coefficient	−34.9	16.9
P value	0.045	0.306

Conclusion: Serum FGF23 levels remain higher than normal in GD patients even after euthyroid status achieved. Underlying mechanisms warrant further investigations. Data are presented as mean±S.D. if the continuous variable is normally distributed, and as median (interquartile range) if not normally distributed. Corrected calcium was calculated as follows: serum calcium (mg/dL) +0.8 * (four – albumin). P values were calculated by t-test for continuous variables and by chi-squared test for categorical variables. FGF23 was log-transformed to become normally distributed for t-test.

Endocrine Abstracts

P1030

Fibroblast growth factor 23 is elevated in patients with euthyroid Graves’ disease

Chia-Hung Lin , Shyang-Rong Shih & Keh-Sung Tsai

Volume 56

20th European Congress of Endocrinology

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