What Is Vitamin D? Is It a Hormone or Vitamin, Uses Of Vitamin D

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Vitamin D – Overview 

Vitamin D is regarded for its role in maintaining bone health. Vitamin D deficiency is a widespread problem which manifests as several symptoms that can have severe impacts.

It is crucial to remember that people with vitamin D insufficiency should be aware of other health risks in addition to bone health issues like fractures. Other illnesses affect the autoimmune, cardiovascular and even neurologic systems. Chronic pain (cancer, musculoskeletal, fibromyalgia) is also noticeable.

According to current research, vitamin D functions more like a prohormone or multifunctional hormone. 

Recent evidence of vitamin D’s extraskeletal effects has added to its early use as a critical skeletal component. This is due to the various body functions performed by vitamin D. 

Pathophysiology of Vitamin D 

vitamin d

Vitamin D intake in sufficient quantities is essential for maintaining good health. A PubMed article titled ‘Vitamin D: Vitamin or Hormone?’ states that vitamin D resembles adrenal and sex hormones and shares a similar chemical structure with steroid hormones. Dietary sources and supplementation are two ways to obtain vitamin D. The body also produces an endogenous form. However, none of these forms is biologically active. 

On exposure to ultraviolet B radiation or sunshine, the skin begins to produce the most prevalent form, cholecalciferol or vitamin D3. Plants, fortified foods and some fish contain ergocalciferol or vitamin D2.

Before being used by the body, vitamin D undergoes two processes known as hydroxylation. This activates the vitamin for use in the body.

The first conversion of vitamin D into calcidiol, commonly known as 25-hydroxyvitamin D [25(OH)D], takes place in the liver. The biologically active form of calcidiol, known as calcitriol (1,23-dihydroxyvitamin D [1,25(OH)₂D]), is then produced by the kidneys, where it is primarily hydroxylated. Vitamin D circulates after being synthesised by binding to the vitamin D-binding protein (VDBP). 

Depending on how quickly the liver converts dietary and endogenous forms of vitamin D to 25(OH)D, they both have half-lives that range from 12 to 24 hours.

Is Vitamin D a hormone? 

A hormone is referred to as a chemical compound that aids in regulating and managing various bodily functions. It circulates in bodily fluids and is a product of living cells. It has a particular stimulatory effect on the activity of cells that are far from their point of origin. 

Numerous hormones have an effect on certain target cells or organs in areas of the body other than where they are produced or manufactured. The question of whether vitamin D should be classified as a vitamin or a hormone has been the subject of numerous debates.

According to a source, it is a prohormone since the body must first transform the chemical vitamin D into a hormone before it can be used. Certain other sources state vitamin D as a precursor to hormones since it requires sunlight to get activated. 

Further evidence that vitamin D should be considered a hormone rather than a vitamin is the fact that it is the only vitamin that is formed by the body and that it can be produced by it. In contrast, vitamins A, B and C can only be obtained from diet and supplements.

Use of Vitamin D as a hormone 

The vitamin D response to specific elements and the presence of vitamin D receptors (VDRs) in the brain are indications that vitamin D plays a significant role in neurobiological pathways and signalling cascades associated with mental health. A vitamin D deficit can be a hormonal deficiency, as there is evidence that vitamin D participates in the many endocrine pathways. 

On a hormone level, vitamin D has also been discovered to play a crucial role in brain growth. Due to this, many people are utilising vitamin D more as a replacement for hormones than as a vitamin supplement.

Numerous research suggests that taking vitamin D supplements helps with the symptoms of attention deficit hyperactivity disorder (ADHD), depression and autism spectrum disorder (ASD). According to a study, persons with hypovitaminosis D were more likely to experience depression due to “reduced gross morphology, cellular proliferation and growth factor signalling” as well as other hormonal irregularities in the brain connected to the deficit.

In another study, it was shown that participants who did not take 40,000 IU of cholecalciferol supplements once a week for six months had higher rates and more severe depression. This was due to reduced levels of vitamin D. However, it should be highlighted that vitamin D appeared to be better at preventing depression than improving the participants’ pre-existing symptoms.

Dietary sources of Vitamin D 

foods containing vitamin d

Vitamin D is obtained from food sources as well as through supplements though sunlight is the main source of the vitamin. 

Food sources of vitamin D 

  • Mushroom
  • Fish (not just fatty fish), including eel, tuna, salmon, cod, trout, mackerel
  • Egg yolks
  • Liver offal 

Vitamin D is added to some foods and is available as fortified food. Foods such as milk, breakfast cereals, margarine and orange juice are fortified with vitamin D.


Vitamin D is acquired through exposure to sunlight as well as from dietary sources. Exposure to ultraviolet B radiation from sunlight makes the skin produce cholecalciferol, or vitamin D3. Vitamin D3 is the most common type of vitamin D. 

Nevertheless, it is believed that vitamin D functions more like a prohormone or hormone with several functions. This is because vitamin D has a role in numerous bodily functions. Vitamin D is an essential nutrient to maintain optimal health. Vitamin D is actually a vitamin but functions similarly to a hormone. This is the only vitamin formed by the body and produced by it, whereas vitamins A, B and C can only be obtained from diet and supplements.


How is vitamin D different from vitamins?

Unlike most other vitamins, vitamin D is absolutely unique. In actuality, it’s a steroid hormone made from cholesterol when the skin is exposed to the sun. Since it may be generated endogenously through ultraviolet skin exposure, vitamin D is frequently referred to as “the sunshine vitamin” despite the fact that it is not an actual vitamin. It is a steroid hormone that has three different versions that hydroxylases sequentially produce. This is the only vitamin that is formed by the body.

What vitamins are hormones? 

According to an NCBI article, ‘Vitamins as hormones’, vitamins A and D are the first set of substances that have been found to exhibit skin hormone-like properties, including organised metabolism, activation, inactivation and removal in tissue-specific specialised cells and release in the circulation.

Why is vitamin D considered a hormone? 

According to certain theories, vitamin D functions more like a prohormone or multifunctional hormone. This is so because vitamin D helps with many body functions.

What is the difference between a vitamin and a hormone?

The main difference between a hormone and a vitamin is that a hormone is an organic compound that one tissue secretes into the bloodstream to trigger a particular physiological response in another tissue, whereas a vitamin is a micronutrient that must be consumed in sufficient amounts to support a healthy metabolism.


The Information including but not limited to text, graphics, images and other material contained on this blog are intended for education and awareness only. No material on this blog is intended to be a substitute for professional medical help including diagnosis or treatment. It is always advisable to consult medical professional before relying on the content. Neither the Author nor Star Health and Allied Insurance Co. Ltd accepts any responsibility for any potential risk to any visitor/reader.

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