The traditional model for hormonal regulation is based on homeostatic control [ 24], by which the bioavailability of a hormone is adjusted to regulate its action.
The results of hormone assays indicated that bioavailability of steroid hormones remained relatively constant, regardless of the IVM system used.
We present the results of a new analysis of our study on the effect of metformin on the bioavailability of sex hormones.
They can function directly on genes and/or indirectly, affecting, for example, the bioavailability of other hormones.
Furthermore, insulin and IGF-1 both stimulate the synthesis of sex steroids and inhibit the synthesis of their plasma carriers, thus enhancing the bioavailability of sex hormones (31).
These findings support that in addition to its action on bioavailability of sex hormones, there is a new pathway by which sex steroids may act on osteoblasts.
Alternatively, there is some evidence that endocrine disruptors, including PFOS, bind to sex hormone binding globulin (SHBG) (Jones et al. 2003), and displacement of reproductive hormones from SHBG binding sites could alter bioavailability of circulating hormones (Déchaud et al. 1999).
Moreover, adipokine-mediated insulin resistance triggers compensatory hyperinsulinemia, which exerts powerful mitogenic procancer effects directly, and also indirectly by increasing the bioavailability of sex hormones and insulin-like growth factor (IGF -1, and the ovarIGF -1oduction of androgens.
Because progesterone and cortisol bind to CBG with about equal affinity [ 84], the exponential rise in circulating progesterone that occurs in late gestation competes with cortisol for CBG binding sites, dynamically affecting the bioavailability of both hormones.
