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Related Concept Videos

Role of Vitamins in Maintaining Bone Health01:25

Role of Vitamins in Maintaining Bone Health

The growth and maintenance of bone are regulated by a combination of nutritional factors, including vitamins, such as vitamin A, B12, C, D, and K.
Vitamin A
Vitamin A is involved in the process of bone remodeling. Retinoic acid, the active metabolite of Vitamin A, has nuclear receptors in osteoblasts and osteoclasts, which are involved in bone remodeling.
Vitamin B12
Vitamin B12 acts as a cofactor during the formation of osteoblast-related proteins, such as osteocalcin. Vitamin B12 plays a role...
Skeleton and Calcium Homeostasis01:21

Skeleton and Calcium Homeostasis

Calcium is not only the most abundant mineral in bone but also the most abundant mineral in the human body. Calcium ions are needed for bone mineralization, tooth health, heart rate regulation and strength of contraction, blood coagulation, the contraction of smooth and skeletal muscle cells, and the regulation of nerve impulse conduction. The average calcium level in the blood is about 10 mg/dL. When the body cannot maintain this level, a person will experience hypo or hypercalcemia.
Role of Skin in Vitamin D Synthesis01:23

Role of Skin in Vitamin D Synthesis

The skin plays a crucial role in the synthesis of vitamin D, a vital nutrient for various physiological processes in the body. Vitamin D is unique because it can be synthesized in the skin through a series of chemical reactions triggered by exposure to ultraviolet B (UVB) radiation from sunlight.
The solar UV B rays (290-315 nm) are absorbed by the skin, and 7-dehydrocholesterol (provitamin D3) photolyzes it to previtamin D3, which undergoes a rapid transformation to vitamin D3(cholecalciferol).
Bone Disorders01:29

Bone Disorders

Aging and its effect on bone remodeling is the most common cause of bone disorders. In young and healthy people, bone deposition and resorption happen at an equal rate to maintain optimal bone health.
Bone deposition is also affected by the levels of sex hormones like estrogen and testosterone that promote osteoblast activity and bone matrix synthesis. When the level of these hormones decreases due to aging, it causes a reduction in bone deposition. As a result, bone resorption by osteoclasts...
Menopause01:28

Menopause

Menopause, a natural biological process marking the end of a woman's fertility, typically occurs between the fifth and sixth decade of life. This phase is characterized by the exhaustion of the ovarian follicle pool, leading to less responsive ovaries despite the high levels of Follicle Stimulating Hormone (FSH) and Luteinizing Hormone (LH). The consequential decrease in estrogen production results in symptoms like hot flashes, heavy sweating, headaches, hair loss, muscle pains, vaginal...
Bone Remodeling01:40

Bone Remodeling

Bone remodeling is a continuous and balanced process of bone resorption by osteoclasts and bone formation by osteoblasts. In adults, it helps maintain bone mass and calcium homeostasis. While mechanical stress can stimulate turnover as part of the normal maintenance and reparative process, several hormones also regulate bone remodeling.

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Related Experiment Video

Updated: Jul 6, 2026

A Method of Trigonometric Modelling of Seasonal Variation Demonstrated with Multiple Sclerosis Relapse Data
10:46

A Method of Trigonometric Modelling of Seasonal Variation Demonstrated with Multiple Sclerosis Relapse Data

Published on: December 9, 2015

Plasma 1,25(OH)2D levels decrease in postmenopausal women with hypovitaminosis D.

Lars Rejnmark1, Peter Vestergaard, Lene Heickendorff

  • 1Department of Endocrinology, Aarhus University Hospital, Aarhus Sygehus, Tage-Hansens Gade 2, DK-8000 Aarhus, Denmark. rejnmark@post6.tele.dk

European Journal of Endocrinology
|March 26, 2008
PubMed
Summary
This summary is machine-generated.

Calcidiol (25OHD) levels influence active vitamin D production in postmenopausal women. Vitamin D insufficiency is indicated by 25OHD levels below 80 nmol/l, impacting calcium homeostasis.

Related Experiment Videos

Last Updated: Jul 6, 2026

A Method of Trigonometric Modelling of Seasonal Variation Demonstrated with Multiple Sclerosis Relapse Data
10:46

A Method of Trigonometric Modelling of Seasonal Variation Demonstrated with Multiple Sclerosis Relapse Data

Published on: December 9, 2015

Area of Science:

  • Endocrinology
  • Nutritional Science
  • Bone Metabolism

Background:

  • Calcidiol (25OHD) is linked to parathyroid function and calcium homeostasis, despite calcitriol (1,25(OH)2D) being the active form.
  • Low 25OHD levels are associated with increased risks of cancer, diabetes, and myopathy.

Purpose of the Study:

  • To investigate the relationship between plasma concentrations of 25OHD, 1,25(OH)2D, and parathyroid hormone (PTH).
  • To determine the threshold for vitamin D insufficiency in postmenopausal women.

Main Methods:

  • Cross-sectional study design.
  • Analysis of fasting plasma samples from 315 healthy postmenopausal women.
  • Measurement of plasma 25OHD, 1,25(OH)2D, and PTH concentrations.

Main Results:

  • Plasma 1,25(OH)2D levels showed a concentration-dependent relationship with plasma 25OHD levels (P<0.001).
  • 1,25(OH)2D levels were approximately one-third lower in subjects with 25OHD levels below 25 nmol/l compared to those above 80 nmol/l (P<0.01).
  • The association between 25OHD and 1,25(OH)2D was most pronounced below 80 nmol/l; PTH was a minor predictor of 1,25(OH)2D.

Conclusions:

  • The conversion of 25OHD to active vitamin D in postmenopausal women is substrate-dependent.
  • Vitamin D insufficiency should be considered when 25OHD levels fall below 80 nmol/l.