No significant differences in CTX (PKU: 1.84 ± 0.24 ng/mL, Co: 1.69 ± 0.58 ng/mL, p = 0.502, d = 0.295), OCN (PKU: 13.5 [12.0–17.1] ng/mL, Co: 14.4 [12.9–17.3] ng/mL, p = 0.714, r = −0.087), uOCN (PKU: 21.5 [10.6–31.6] ng/mL, Co: 31.4 [24.0–33.8] ng/mL, p = 0.235, r = −0.272) and the ratio of uOCN/OCN (PKU: 1.33 [0.77–1.95], Co: 1.76 [1.18–2.14], p = 0.416, r = −0.201) were detected between groups (Figure 3). Here, CYP27A1 is linked to phenylketonuria.