Follistatin

Follistatin is a binding protein for the activin and inhibin family of hormones, regulating their biological activity.
https://www.ncbi.nlm.nih.gov/pubmed/9886507
Does this mean that it's like SHBG but for activins/inhibins?

suggests that all activin A in the circulation is bound to follistatin in males.
https://www.ncbi.nlm.nih.gov/pubmed/9886507