Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (1259 page)

   Factors that increase triglyceride levels include food and alcohol intake (should be 12-hour fast [24 hours for alcohol]); corticosteroids, protease inhibitors for HIV, beta blockers, and estrogens; pregnancy; acute illness; smoking; and obesity.

   Factors that decrease triglyceride levels include exercise and weight loss.

   Diurnal variation causes triglycerides to be lowest in the morning and highest around noon.

   Other Considerations

   Serum for triglyceride and for calculating LDL-C should follow a 12-hour fast.

Suggested Reading

National Institutes of Health, National Heart Lung and Blood Institute’s National Cholesterol Education Program.
http://www.nhlbi.nih.gov/about/ncep/
. Accessed November 18, 2010.

TRIIODOTHYRONINE (T
₃
)

   Definition

   T
₄
(thyroxine) is converted to T
₃
in peripheral tissues; approximately 20% is synthesized by follicular cells. Most T
₃
is transported bound to protein; only 0.3% is in free unbound state (see Table 16.76 and Fig. 16.5).

   
Normal range:

   Total T
₃
: 87–178 ng/dL

   Free T
₃
: 2.5–3.9 pg/mL

   Use

   Diagnosis of T
₃
thyrotoxicosis (when TSH is suppressed but T
₄
is normal) or cases in which FT
₄
is normal in the presence of symptoms of hyperthyroidism.

   Evaluating cases in which FT
₄
is borderline elevated.