Table 3.
Hormone binding proteins found in human serum.
| Binding protein | Metabolites | Percent free | |
|---|---|---|---|
| DBP 4.5–5.5 μMa |
Total 25(OH)D 25–75 nMa |
Free 25(OH)D 5–20 pMa |
0.02 |
| Total 1,25(OH)2D 50–198 pMb |
Free 1,25(OH)2D 325–525 fMc |
0.5 | |
| TBG 241–722 nMb |
Total T4 58–154 nMb |
Free T4 11–23 pMb |
0.02 |
| Total T3 1.1–2.8 nMb |
Free T3 3.0–6.8 pMb |
0.3 | |
| SHBG 16.5–55.9 nMb(male) |
Male total T 9.2–31.8 nMb |
Male free T 30–87 pMb |
0.3 |
| Male total E2 28–156 pMb |
Male free E2 <1.7 pMd |
1 | |
| SHBG 24.6–122.0 nMb (female) |
Female total T 0.3–1.7 nMb |
Female free T <15 pMb |
0.9 |
| Female total E2 46–609 pMb |
Female free E2 1.6–18.5 pMd |
3 | |
a
Nielson et al. (88).
c
Bikle et al. (89).
Vitamin D binding protein (DBP), thyroxine binding globulin (TBG), and sex hormone binding globulin (SHBG) are tabulated with their serum concentration levels. The respective metabolite concentrations total, free and percent free are also presented. Albumin can bind all the hormones listed and transthyretin can bind T4 albeit at lower affinity compared to their primary carrier proteins. The bioavailable concept has been applied to these hormones and comprise the sum of albumin-bound-hormone and free hormone.