Vitamin D Council Glossary

# A B C D E F G H I J–K L M N O P R S T U V
T lymphocytes (T cells)
Lymphocytes that play a central role in cell-mediated immunity and are distinguishible from other lymphocyte types, such as B cells and NK cells, because of a receptor on their cell surface called the T cell receptor (TCR). T cells originate in the thymus.
Triiodothyronine. see thyroid hormone.
Thyroxine. see thyroid hormone.
Also called 1α,24-dihydroxyvitamin D3. see vitamin D analogues.
An isomer of ergosterol that forms vitamin D2 when irradiated with ultraviolet light.
Tazarotene-induced gene-1 (TIG1)
Protein which has been implicated in suppressing an early stage of prostrate tumor development when exposed to vitamin D and retinoic acid (a derivative of vitamin A).
Toxic equivalent.
Anabolic steroid hormone that is the principal male sex hormone, though it plays a key role in the health and well-being of both males and females. Testosterone affects libido, energy, and immune function as well as helps to protect against osteoporosis.
Sub-type of T cell known as a T-helper lymphocyte.
The thymus is a lymphoid organ situated in the center of the upper chest just behind the breastbone. It is in the thymus that lymphocytes mature, multiply, and become T cells.
One of the largest endocrine glands, the thyroid controls (through the production of thyroid hormone) how quickly the body burns energy and makes proteins. It controls how sensitive the body should be to other hormones and, through the production of calcitonin, plays a role in calcium homeostasis.
Thyroid hormone
Hormone produced by the thyroid gland that helps control metabolism, body temperature, and the rate of function of many other bodily systems. Needed for normal development of the brain, especially during the first 3 years of life. The two thyroid hormones are thyroxine (T4) and triiodothyronine (T3).
Thyroid-stimulating hormone (TSH)
Tropic hormone that activates the production of thyroid hormone in the thyroid gland. TSH is produced by the pituitary gland when the hypothalamus releases a substance called thyrotropin-releasing hormone (TRH).
The larger and stronger of the two bones in the leg below the knee in vertebrates, connects the knee with the ankle bones.
Tissue inhibitor of metalloproteinase 1. TIMP-1 is a contributory factor to fibrosis of a variety of organs, including the liver.
Transfer of genetic information from DNA into RNA.
Transcription factor
Protein that works in concert with other proteins to either promote or suppress the transcription of genes.
Trimethylglycine (TMG)
Also known as betaine. A substance manufactured by the body to help break down homocysteine.
Tropic hormone
Anterior pituitary-secreted hormones. Regulate the activity of various endocrine glands.
Tuberculosis (TB)
Deadly infectious disease that is caused by the mycobacterium called Mycobacterium tuberculosis or Mycobacterium bovis. Tuberculosis usually affects the lungs (pulmonary TB). Can also the central nervous, lymphatic, circulatory, and genitourinary systems, as well as bones, joints, and the skin.
Tumor Necrosis Factor (TNF)
Cytokine that can cause apoptosis.
also known as L-tyrosine. Tyrosine is one of the 20 amino acids that are used by cells to synthesize proteins.
Tyrosine hydroxylase
Enzyme responsible for catalyzing the conversion of the amino acid L-tyrosine to dihydroxyphenylalanine.

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