While there are hundreds, there are only 4 that are essential to life and if you don’t have them, you die. We’ve only talked about two of them in detail, which is insulin and the glucocorticosteroids, such as cortisol. We can’t explain cortisol really well, and it’s weird because it breaks down protein, reduces immune system and reduces inflammatory response. Don’t think for a moment we understand how everything works but we do know that someone will die within a week without this hormone.
Four Hormones Essential to Life
- Parathyroid Hormone (PTH)
- Glucocorticosteroids (Cortisol)
- Mineralcorticosteroids (Aldosterone)
1. Insulin is the only hormone that in its totality, is anabolic in its actions. That is to say, purely growth, healing and repair occur by way of glycogenesis, lipogenesis, and protein synthesis. While there are some hormones that provide catabolic and some that do a mixture, this is exclusively anabolic and we can’t live without it. The hormone that has the exact reverse action and is totally catabolic in nature is glucagon. It exclusively promotes glycogenolysis, lipolysis, protein catabolism, and gluconeogenesis.
Very Relevant to this: How Glucose Levels are Regulated in the Blood Stream. Insulin and glucagon are important in shifting metabolic pathways between absorptive and postabsorptive states, which maintains the appropriate plasma levels of nutrient molecules.
2. Parathyroid Hormone (PTH) from the parathyroid glands regulates calcium level and it’s needed for muscle contraction and blood clotting. It’s critical to maintaining plasma concentration of Ca+2. PTH is essential for life because of calciums effect on neuromuscular capability. In the absence of PTH, death rapidly occurs from asphyxiation caused by pronounced spasms of the respiratory muscles.
Parathyroid Hormone activates osteoclasts which break down bone tissue and release the minerals, resulting in a transfer of calcium from bone to the blood. This is known as bone resorption.
Calcitonin (aka thyrocalcitonin) is the reverse of PTH. Calcitonin activates osteoblasts to form bone tissue by transferring calcium from the bloodstream to the bone tissue. This is known as ossification (or osteogenesis, synonymous with bone tissue formation).
3. Cortisol, the primary glucocorticosteroid secreted by your adrenal cortex, increases catabolism of proteins and thus, the plasma concentrations of glucose, fatty acids, and amino acids above normal. We talked about cortisol in great detail already when we talked about how ACTH releases glucocorticosteroids such as Cortisol. Although these actions destabilize the concentrations of these molecules, they indirectly contribute to homeostasis by making the molecules available as energy sources or building blocks for tissue repair to help the body adapt to stressful situations. Review the topic specifically on stress and cortisol!
4. Aldosterone, the primary mineralcorticosteroid secreted by your adrenal cortex, is absolutely essential to your life. Without it, you will die within a week. It’s essential for Na+ and K+ balance. Because of sodiums osmotic effect, sodium balance is critical to maintaining the proper ECF volume and arterial blood pressure. This action is essential for life. Without aldosterone’s sodium and water-conserving effect, so much plasma volume would be lost in the urine that death would quickly occur. Maintaining potassium ion balance is also essential for homeostasis because changes in ECF K+ profoundly impact neuromuscular excitability, most importantly of the heart.
The absolutely unbelievable, fantastic, incredible, homeostatic reflex involved with this is called the renin angiotensin system or renin-angiotensin-aldosterone reflex (or RAA pathway) which we’ll dive into next.