Table 1. Clinical characteristics of amenorrheic athletes (AA), eumenorrheic athletes (EA) and non-athletes (NA).

	AA N = 38	EA N = 24	NA N = 23	ANOVA P-value	AA vs. EA P-value	AA vs. NA P-value	EA vs. NA P-value
Age (years)	19.3±2.0	18.0±2.0	19.1±1.7	0.04	0.03	0.86	0.16
Bone age (years)	17.4±1.0	17.2±1.2	17.5±1.1	0.49	0.60	0.91	0.50
Tanner stage distribution (T2, 3, 4, 5)	2.6%, 10.5%, 15.8%, 71.1%	0%, 4.2%, 20.8%, 75.0%	0%, 8.7%, 0%, 91.3%	0.31	0.66	0.17	0.06
Age at menarche (y)	14.0±1.8	12.8±1.4	12.2±1.5	0.0004	0.02	0.0004	0.45
Days since last menses	165 (24–360)	-	-	-
BMI (kg/m2)	20.3±2.2	22.4±2.3	21.5±2.5	0.005	0.004	0.15	0.43
Height (cm)	165.7±6.7	165.7±8.2	162.6±7.2	0.23	0.98	0.37	0.35
Fat mass (kg)	11.7±3.7	15.1±4.4	16.0±4.9	0.0004	0.009	0.001	0.79
Lean mass (kg)	43.5±5.7	46.3±7.7	40.5±4.4	0.006	0.18	0.15	0.004
Percent body fat	20.3±5.1	23.5±3.8	27.0±5.2	<0.0001	0.03	<0.0001	0.04
Hours/week of exercise	10.4±5.6	11.0±4.9	0.8±0.7	<0.0001	0.87	<0.0001	<0.0001
Resting energy expenditure (calories)	1247±183	1444±218	1255±193	0.0005	0.0007	0.99	0.004
REE/lean mass (cal/kg)	28.9±3.8	31.6±5.3	31.2±4.9	0.04	0.06	0.13	0.95
History of fractures	50%	16.7%	8.7%	0.0007	0.01	0.0009	0.67
25(OH) vit D (ng/ml)	38.3±12.5	30.5±13.8	21.1±7.8	<0.0001	0.04	<0.0001	0.03
Irisin (mcg/ml) §	3.20 (2.58–3.53)	3.85 (3.50–4.80)	3.60 (3.30–4.20)	0.0004	0.001	0.009	0.83
FGF21 (pg/ml) §	54.5 (32.3–102.3)	94.5 (60.3–189.8)	132.0 (109.0–230.0)	0.0001	0.02	<0.0001	0.26

Mean ± SD or Median (Interquartile Range); FGF21: fibroblast growth factor 21; AA: amenorrheic athletes; EA: eumenorrheic athletes; NA: non-athletes.

^§P values reported for log converted data.