<P> A steroid hormone is a steroid that acts as a hormone . Steroid hormones can be grouped into two classes: corticosteroids (typically made in the adrenal cortex, hence cortico -) and sex steroids (typically made in the gonads or placenta). Within those two classes are five types according to the receptors to which they bind: glucocorticoids, mineralocorticoids (corticosteroids), androgens, estrogens, and progestogens (sex steroids). Vitamin D derivatives are a sixth closely related hormone system with homologous receptors . They have some of the characteristics of true steroids as receptor ligands . </P> <P> Steroid hormones help control metabolism, inflammation, immune functions, salt and water balance, development of sexual characteristics, and the ability to withstand illness and injury . The term steroid describes both hormones produced by the body and artificially produced medications that duplicate the action for the naturally occurring steroids . </P> <P> The natural steroid hormones are generally synthesized from cholesterol in the gonads and adrenal glands . These forms of hormones are lipids . They can pass through the cell membrane as they are fat - soluble, and then bind to steroid hormone receptors (which may be nuclear or cytosolic depending on the steroid hormone) to bring about changes within the cell . Steroid hormones are generally carried in the blood, bound to specific carrier proteins such as sex hormone - binding globulin or corticosteroid - binding globulin . Further conversions and catabolism occurs in the liver, in other "peripheral" tissues, and in the target tissues . </P> <P> A variety of synthetic steroids and sterols have also been contrived . Most are steroids, but some nonsteroidal molecules can interact with the steroid receptors because of a similarity of shape . Some synthetic steroids are weaker or stronger than the natural steroids whose receptors they activate . </P>

What type of hormone can cross a cell membrane easily