Vitamin D


Getting some sun to "soak up some Vitamin D" is something you probably hear regularly during warmer months. However, the truth is, this often-misunderstood "vitamin" is not a vitamin — it is a prohormone. Prohormones are substances that the body converts to a hormone. In fact, unlike other vitamins, only about 10 percent of the vitamin D the body needs comes from food (such as dairy products and oily fish), and the rest the body makes for itself. Understanding this hormone and the role it plays in the body will help you make informed health decisions.

Vitamin D is a hormone the kidneys produce that controls blood calcium concentration and impacts the immune system. It is also known as calcitriol, ergocalciferol, calcidiol and cholecalciferol. Of those, calcidiol is the form doctors most commonly focus on when measuring vitamin D levels in the blood.

The body makes vitamin D in a chemical reaction that occurs when sunlight hits the skin. This reaction produces cholecalciferol, and the liver converts it to calcidiol. The kidneys then convert the substance to calcitriol, which is the active form of the hormone in the body.

Vitamin D has its effects by binding to a protein (called the vitamin D receptor). This receptor is present in nearly every cell and affects many different body processes. 

What does vitamin D do?

Vitamin D helps the body absorb calcium so that blood calcium levels are at the ideal point. This helps enable the mineralization of bone that is required for strong, healthy bones. Yet this is just one function of the hormone.

Vitamin D deficiency has been linked to a variety of health concerns, which points to a wide range of vitamin D functions, although research is still underway into why the hormone impacts other systems of the body. For instance, too little vitamin D makes an individual more prone to infections and illness, cardiovascular disease, and mental illnesses — including mood disorders like depression. Studies also show that people who have low vitamin D levels are more likely to be obese. Researchers have found that vitamin D helps regulate adrenaline, noradrenaline (also called norepinepherine), and dopamine production in the brain; as well as helping to protect from serotonin depletion. For this reason, low vitamin D levels increase an individual's risk of depression significantly. A better understanding of vitamin D function is necessary to fully comprehend how it is linked to so many health concerns.

Problems Associated with Vitamin D

An increased focus on protecting the skin from sun damage and a change from an outdoor lifestyle to an indoor lifestyle in recent generations has led to a serious problem with vitamin D deficiency in many developed parts of the world. Too little vitamin D means the bones will not be able to grow strong, leading to problems like rickets for children or osteoporosis for adults. Due to the weakening of bones, individuals with low vitamin D levels are more prone to falling. Low vitamin D levels can also cause a poorly functioning immune system, cardiovascular disease, depression, development of diabetes, and multiple sclerosis. It has also been linked to certain types of cancer.

Even though people rarely struggle with dangerously high levels of vitamin D. If your body has too much of the vitamin it can also cause calcium levels in the blood to increase, causing hypercalcaemia. This condition can trigger confusion, depression, headaches, constipation, nausea, and feelings of thirst.

Questions to ask your doctor

  • What are my vitamin D levels? What should they be?
  • How can I get more vitamin D?
  • What type of supplement is the best?
  • How much vitamin D should I be taking?

Because vitamin D is a hormone, an endocrinologist is the best type of doctor to discuss your vitamin D levels with. To take the next step, find an endocrinologist near you.

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The Hormone Health Network is the public education affiliate of the Endocrine Society dedicated to helping both patients and doctors find information on the prevention, treatment and cure of hormone-related conditions.

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