Vitamin D Council Glossary

T-lymphocytes (T-cells)

Lymphocytes that play a central role in cell-mediated immunity and are distinguishable 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.

Tacalcitol (1α,24-dihydroxyvitamin D3)

Vitamin D analog.

Tachysterol

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 prostate tumor development when exposed to vitamin D and retinoic acid.

Testosterone

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.

Th1

A type of T-helper lymphocyte.

Thymus

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.

Thyroid

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. 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. Thyroid-stimulating hormone (TSH) is produced by the pituitary gland when the hypothalamus releases a substance called thyrotropin-releasing hormone (TRH).

Tibia

The larger and stronger of the two bones in the leg below the knee that connects the knee with the ankle bones in vertebrates.

Tissue inhibitor of metalloproteinase 1 (TIMP-1)

Contributory factor to fibrosis of a variety of organs, including the liver.

Toxic equivalent (TEQ)

Toxicity of a less toxic compound expressed as a fraction of the toxicity of another compound that is considered most toxic.

Transcription

Transfer of genetic information from DNA to RNA.

Transcription factor

Protein that works in concert with other proteins to either promote or suppress gene transcription.

Trimethylglycine (TMG,betaine)

Substance manufactured by the body to help break down homocysteine.

Tropic hormone

Anterior pituitary-secreted hormones that 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) but can also the CNS, lymphatic system, circulatory system, genitourinary system, an other areas of the body.

Tumor Necrosis Factor (TNF)

Cytokine that can cause apoptosis.

Tyrosine (L-tyrosine)

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.