check estrogen metabolites, cortisol, gh, progesterone, and also nutrient absorption, high fiber , low fat, low protein diets, malfunctioning liver.
Medicines such as thyroid t3, and estrogens (xeno estrogens) can raise shbg,
I have driven my shbg down into the ground and shbg is still high
Shbg is just a symptoms of the cause.
If last resort danazol 25 mgs ED or proviron 50 mgs daily works great as well.