GENERAL HISTOLOGY

Detailed explanation-1: -Steroid hormones are generally thought to pass easily across a plasma membrane into a cell, interacting once inside with soluble nuclear receptors, but recent experiments have demonstrated the importance of membrane-bound receptors in mediating the activity and the metabolism of steroid hormones.

Detailed explanation-2: -Steroid hormones are lipid soluble, allowing them to diffuse through the plasma membrane. The actions of steroid hormones can be exerted via nuclear hormone receptors (which are typically slow genomic actions).

Detailed explanation-3: -According to the free hormone hypothesis, because of their hydrophobicity, steroids are able to freely diffuse across lipid bilayers; however, megalin-dependent endocytosis has been shown to be at least partly responsible for the uptake of sex hormones and vitamin D3.

Detailed explanation-4: -Because all steroid hormones are derived from cholesterol, they are not soluble in plasma and other body fluids. As a result, steroids are bound to transport proteins that increase their half-life and insure ubiquitous distribution.