Serum levels of fetal antigen 2 in hyperthyroidism and primary hyperparathyroidism.

Serum concentration of fetal antigen 2 (FA2) in patients with hyperthyroidism (n = 18) (median: 12.9 mAU/l; range: 3.2-22.4 mAU/l) was significantly (p < 0.002) higher than in age- and sex-matched healthy controls (median: 4.1 mAU FA2/l; range: 2.4-10.0 mAU FA2/l). Serum FA2 was positively correlated with thyroxine (T4) (Rs = 0.51; p < 0.05), triiodothyronine (T3) (Rs = 0.64; p < 0.01), bone-Gla protein (BGP) (Rs = 0.70; p < 0.01), total alkaline phosphatase (total-AP) (Rs = 0.62; p < 0.01), bone isoenzyme alkaline phosphatase (bone-AP) (Rs = 0.63; p < 0.01), N-terminal procollagen type III (PIIINP) (Rs = 0.65; p < 0.01) and urine OH-proline (OHP) (Rs = 0.79; p < 0.01). In patients with hyperparathyroidism the pretreatment levels of FA2 (n = 8) (median: 17.6 mAU/l; range: 5.2-35.0 mAU/l) were significantly (p < 0.001) higher than those of age- and sex-matched controls (median: 3.7 mAU FA2/l; range: 3.4-9.0 mAU/l). The pretreatment level of FA2 was positively correlated with the parathyroid hormone (PTH) (Rs = 0.80; p < 0.05). Following surgical treatment the serum concentrations of FA2, PTH, and BGP decreased compared to pretreatment levels and the fall in these three parameters revealed parallelism. These data indicate that serum FA2 can be used as a marker in the evaluation of metabolic bone diseases.