Thanks to David T. Zava, Ph.D. for this technical explanation:

The Steroid Hormone Family
Some hormones are composed of large proteins and others of small fatty substances derived from cholesterol. One class derived from cholesterol belongs to a family of hormones termed steroids. The steroid family is broken down into five major categories including the estrogens (estradiol, estriol, estrone), progesterone, androgens (DHEA, testosterone, androstenedione), glucocorticoids (cortisol, cortisone), and mineralcorticoids (aldosterone). Cholesterol is converted to the mother steroid hormone, pregnenolone, which is then further converted in the ovaries, testes, and adrenal glands to the other hormones, as directed by protein hormone signals from the brain.

The Brain Controls Steroid Hormone Synthesis
How much, and what type of steroid hormone is produced is controlled by specific chemical messages from the brain. In women, the brain message FSH (follicle stimulating hormone) signals the ovaries to produce estrogens. LH (luteinizing hormone), produced during the second half of the menstrual cycle then signals the ovaries to produce progesterone, which helps to balance and slow estrogen-stimulated growth. In men, LH signals the testes to manufacture testosterone. Stress, in the form of physical, emotional, or dietary, signals the brain to produce ACTH (adrenocorticotropin hormone), which in turn signals the adrenal glands to produce cortisol that regulates glucose levels in the blood and activates immune response to foreign invaders such as viruses and bacteria.

Why only some tissues respond to hormones

Once the steroid hormones are released into the bloodstream they are carried within seconds to different tissues throughout the body. While all cells of the body are bathed in the steroid hormones, only some respond to the hormone signal. For example, cells in the breast, uterus, and brain respond to estrogens, whereas muscle cells do not.

Response to a specific hormone requires the presence of a specific steroid-binding receptor protein present within the cell. When the steroid enters the cell it binds and activates the receptor, which in turn, activates unique gene sites that orchestrate the production of new cell products such as enzymes, structural proteins, and new receptors to other hormones. For example, estrogens bind to estrogen receptor in cells of the breast and uterus and trigger the synthesis of growth-promoting factors, leading to cell growth and division. Estrogens also induce receptors for progesterone, allowing subsequent cell response to progesterone produced during the luteal phase of the menstrual cycle. Progesterone, through its own receptor system, invokes the synthesis of its own unique cell products, including secretory proteins (needed for the fertilized egg to adhere to the wall of the uterus) and proteins that down-regulate the receptor for estrogen, shutting off further tissue response to estrogens. In the brain, estrogens promote synthesis of neurotransmitters such as serotonin, essential for normal brain function.

Each of the different steroid hormones is responsible for regulating thousands of unique and different cellular products needed for general cell maintenance and repair as well reproduction, immune modulation, and brain function. In short, steroid hormones are powerful molecules essential for maintaining physical and mental health. So it is not difficult to see why an imbalance of any one hormone can throw your physical and mental health out of balance, causing aggravating and even serious health problems

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