SHBG and TSH-secreting pituitary adenoma: However, due to inhibition of its synthesis, SHBG can be normal in patients with mixed GH/TSH-secreting pituitary tumors or TSHoma with coincident insulin resistance or in microadenoma cases (59); conversely, other factors (oral estrogen therapy, anorexia) can cause elevated SHBG in RTHβ (2).