T Cell
A type of lymphocyte (disease-fighting white blood cell). The "T" stands for the thymus, where T cells mature. T cells include CD4 cells and CD8 cells, which are both critical components of the body's immune system.
See Also:   CD4 Cell
                   CD8 Cell
                   Lymphocyte

T Lymphocytes
See:    T Cell

T Tropic Virus
See:    X4-Tropic Virus

TAMs
See: Thymidine Analogue Mutations

Tanner Staging
A method for determining an adolescent's stage of sexual development, irrespective of chronological age. In HIV treatment, Tanner staging is used to determine the appropriate treatment guidelines to follow: adult, adolescent, or pediatric.

TAT
See: Total Adipose Tissue

TB
See: Tuberculosis

TDM
See: Therapeutic Drug Monitoring

TEN
See: Toxic Epidermal Necrolysis

Teratogenic
Causing harm to a fetus by interfering with normal prenatal development. Many drugs, including some anti-HIV drugs, are teratogenic when taken by pregnant women.

Testosterone
A hormone necessary for normal male sexual development and functioning and also important in maintaining muscle strength and mass. Testosterone is sometimes used for the treatment of HIV-related wasting syndrome and to increase muscle mass and decrease body fat in people with HIV. Testosterone replacement therapy is also used to raise testosterone levels in people with HIV-related hypogonadism.
See Also:   Wasting Syndrome
                   Hypogonadism

Therapeutic Drug Monitoring (TDM)
Measurement of anti-HIV drug levels in an individual's blood. These measurements are then used to make appropriate adjustments to the dosage of the drug. TDM may help improve the drug's effect and reduce side effects by keeping the blood level in a specific target range. TDM is mainly used for drugs in which small changes in drug levels cause large changes in drug effect.
See Also:   Therapeutic Index

Therapeutic HIV Vaccine
Any HIV vaccine used for the treatment of an HIV-infected person. Therapeutic HIV vaccines are designed to boost an individual's immune response to HIV infection in order to better control the virus. This therapeutic approach is currently being tested in clinical trials.
See Also:   Preventive HIV Vaccine

Therapeutic Index (TI)
A measure of a drug’s ability to achieve the desired effect in an individual. Many anti-HIV drugs have a narrow TI, meaning that small changes in levels of the drug may produce big effects. Doses of these drugs are sometimes adjusted using therapeutic drug monitoring (TDM).
See Also:   Therapeutic Drug Monitoring

Thrombocytopenia
A lower than normal number of blood platelets (cells important for blood clotting).
See Also:   Platelets

Thrush
See:    Candidiasis

Thymidine Analogue Mutations (TAMs)
Mutations in HIV's reverse transcriptase (RT) enzyme that can occur with the use of the NRTIs zidovudine and stavudine. TAMs make HIV resistant to these drugs and may limit a person's treatment options.
See Also:  Nucleoside Analogue Reverse Transcriptase Inhibitor
                   Reverse Transcriptase

Thymus
An organ in the chest behind the breastbone. This organ is an essential part of the immune system because it is the site where infection-fighting T cells develop.
See Also:   T Cell

TI
See: Therapeutic Index

Titer
A laboratory measurement of the amount of a given compound in solution. For example, an antibody titer is the measurement of the amount of a particular antibody in a sample of blood.

Tolerability
Term used to indicate how well a particular medication is tolerated or endured when taken by people at the usual dosage. Good tolerability means that medication side effects don't cause people to stop using the drug.

Tolerance
A decreasing response to repeated doses of a drug, requiring a dose increase to continue the effects of the drug.

Total Adipose Tissue (TAT)
Adipose (fat) tissue is primarily located under the skin (subcutaneous adipose tissue), but also found around internal organs (visceral adipose tissue). Together, these two types of fat tissue are called total adipose tissue. Lipodystrophy, or changes in body fat, are a potential side effect of some anti-HIV drugs, especially PIs and NRTIs.
See Also:   Subcutaneous Adipose Tissue
                   Visceral Adipose Tissue
                   Lipodystrophy

Toxic Epidermal Necrolysis (TEN)
A severe form of Stevens-Johnson syndrome involving at least 30% of the total body skin area.
See Also:   Stevens-Johnson Syndrome

Toxicity
Ability to poison or otherwise harm the body.

Toxoplasmosis
An infection caused by the parasite Toxoplasma gondii. The parasite is carried by cats, birds, and other animals, and is also found in soil contaminated by cat feces and in meat, particularly pork. Infection can occur in the lungs, retina of the eye, heart, pancreas, liver, colon, testes, and brain. Toxoplasmosis of the brain is considered an AIDS-defining condition in people with HIV.

Transcription
One of the steps in the HIV life cycle. Transcription is the process by which the HIV DNA provirus is used as a template to create copies of HIV's RNA genetic material, as well as shorter strands of HIV RNA called messenger RNA (mRNA). HIV mRNA is then used in a process called translation to create HIV proteins and continue the virus's life cycle.
See Also:   Provirus
                   Translation
                   Messenger RNA

Translation
The step in the HIV life cycle that follows transcription. Translation is the process by which the genetic information contained in HIV mRNA is used to build HIV proteins using the host cell's protein-making machinery. Once these HIV proteins are produced, they can combine with copies of HIV's RNA genetic material to form new, complete copies of HIV.
See Also:   Transcription

Transplacental
Across or through the placenta. Usually refers to the exchange of nutrients, waste products, and other materials (for example, drugs or infectious organisms) between the mother and the fetus.

Treatment Failure
A broad term describing failure of an anti-HIV treatment to adequately control HIV infection. The three types of HIV treatment failure are virologic, immunologic, and clinical failure. Factors contributing to treatment failure include poor adherence, drug resistance, and drug toxicity.
See Also:   Virologic Failure
                   Immunologic Failure
                   Clinical Failure

Treatment-Experienced
A term used to describe HIV-infected individuals who are currently being treated with anti-HIV drugs or who have taken anti-HIV drugs in the past.
See Also:   Treatment-Naive

Treatment-Naive
A term used to describe HIV-infected individuals who have never taken anti-HIV drugs.
See Also:   Treatment-Experienced

Triglycerides
Fat-like substances that help transfer energy from food into cells. Triglyceride levels that are too high increase the risk of heart disease and have been associated with diabetes and pancreatitis. Elevated triglyceride levels are a potential side effect of some PIs.

Trough Level
See:    CMIN

Tuberculin Skin Test
A test performed by injecting purified protein derivative (PPD) extract under the skin. A person who receives this test must return to his or her health care provider after 48 to 72 hours so that the skin's reaction can be evaluated. A hard red bump or a swollen area at the injection site indicates that the person has been exposed to the bacterium that causes tuberculosis (TB). Additional tests are required to determine if the person has active TB infection.
See Also:   Purified Protein Derivative
                   Tuberculosis

Tuberculosis (TB)
An infection caused by the bacterium Mycobacterium tuberculosis. TB bacteria are spread through the air when a person with active TB coughs, sneezes, or speaks. Breathing in the bacteria can lead to infection in the air sacs of the lungs. Symptoms of TB in the lungs include cough, tiredness, weight loss, fever, and night sweats. Although the disease usually occurs in the lungs, it may also affect the larynx, lymph nodes, brain, kidneys, or bones. A person with both TB and HIV is more likely to develop tubuerculosis disease than a person infected only with the TB bacterium, and TB is considered an AIDS-defining condition in people with HIV.
See Also:   Tuberculin Skin Test

t.i.d. (tid from Latin ter in die)
Three times a day dosing instructions.