The study found that the immune peptide thymosin‑alpha‑1 is naturally present in male semen and female follicular fluid, and higher levels are linked to better sperm counts, larger semen volume, and more mature eggs. Men and women with infertility tended to have lower levels. While the research is only observational, it suggests that thymosin‑alpha‑1 could serve as a biomarker for reproductive health, but it doesn’t provide a dosing or treatment protocol yet.

High levels of thymosin alpha 1 (T alpha 1) were detected in human seminal plasma and follicular fluid. In the seminal plasma of 19 males studies, T alpha 1 levels varied from 614 to 2,604 pg/mL (mean +/- SD, 1,682.4 +/- 453.9 pg/mL). There was a correlation between the T alpha 1 levels and the total number of sperm in the ejaculate (r = .18) and seminal volume (r = .26). The infertile males, who had low levels of T alpha 1 also demonstrated fewer sperm, reduced motility, and lower semen volume. In follicular fluid collected from 24 follicles of 10 infertile females, T alpha 1 levels varied from 1,019 to 6,384 pg/mL (mean +/- SD, 3,572.8 +/- 1,599.7 pg/mL), which were higher when compared with the corresponding serum levels (mean +/- SD, 1,666.9 +/- 1,378.9 pg/mL). T alpha 1 levels present in follicular fluids which had "immature" oocytes were lower when compared with follicular fluids which had "intermediate" or "mature" oocytes. The immunoreactive T alpha 1 present in seminal plasma of males and in the follicular fluids of females may be involved in some aspect of germ cell maturation and function. The measurement of T alpha 1 levels may be useful in the diagnosis and treatment of male and female infertility, and also as a novel marker for the assessment of maturity of oocytes required for in vitro fertilization-embryo transfer.