noun, plural: steroid hormones
Steroids are organic compounds derived from lanosterol in animals and fungi and from cycloartenol in plants. In animals, the steroids include those found in vertebrates and insects. Steroids in vertebrates, including humans, include cholesterol and steroid hormones.
A steroid hormone is a steroid that acts as a hormone. Steroid hormones include sex steroids (e.g. androgens, estrogens, and progesterones), corticosteroids (e.g. glucocorticoids and mineralocorticoids), and anabolic steroids. They, therefore, are involved in regulating the development of sexual characteristics, inflammation, immune functions, and homeostasis.
Steroid hormones are derived generally from the sterol, cholesterol. Depending on the type, they are produced in the gonads or in the adrenal glands. When they are secreted, they are released into the bloodstream while bound to carrier proteins (e.g. sex hormone-binding globulin for sex hormones, corticosteroid-binding protein for corticosteroids, albumin, etc.). Then, they reach their target cell. In free hormone hypothesis, the steroid hormone is hypothesized to freely pass through the cell membrane of the target cell since they are lipids. Inside the cell, they become active when the carrier protein releases them and bind to the steroid hormone receptors in the nucleus or in the cytosol. This interaction will bring about changes within the cell.
In another hypothesis, the steroid hormone-carrier protein complex docks to megalin, a membrane receptor. This then leads to its endocytosis to be taken inside the target cell. When inside, the complex is brought to the lysosome to degrade the carrier protein and release the steroid hormone into the cytosol. The steroid hormone then exerts its effect on the cell via a genomic pathway.