T4 (thyroxine) is the predominant hormone produced by the thyroid gland. It is an inactive hormone and is converted into its active form, T3 within cells. Free T4 is the non-bound fraction of the total T4 circulating in the blood.

Free T4, or free thyroxine, is an essential thyroid hormone that plays a crucial role in regulating metabolism and overall health. While conventional thyroid function tests typically measure Free T4 in blood samples, it's less common to assess Free T4 in dried urine tests. Dried urine tests are more commonly used to measure certain other hormones and metabolites.

Testosterone is the primary male sex hormone in humans. A healthcare professional may order a free testosterone blood test if you’re experiencing sexual problems or a secondary condition, like hyperthyroidism, is suspected.  

A free testosterone test for men is a critical diagnostic tool in evaluating and managing a variety of health conditions, primarily those related to hormonal balance and reproductive health. Testosterone, a vital male hormone, plays a significant role in several physiological processes including muscle mass and strength, bone density, fat distribution, and sexual function. While total testosterone measures the overall level of the hormone in the blood, free testosterone specifically refers to the fraction of testosterone that is not bound to proteins in the blood and is therefore biologically active and readily available to tissues.

A free testosterone test for men is a critical diagnostic tool in evaluating and managing a variety of health conditions, primarily those related to hormonal balance and reproductive health. Testosterone, a vital male hormone, plays a significant role in several physiological processes including muscle mass and strength, bone density, fat distribution, and sexual function. While total testosterone measures the overall level of the hormone in the blood, free testosterone specifically refers to the fraction of testosterone that is not bound to proteins in the blood and is therefore biologically active and readily available to tissues.

Free Testosterone is the bioavailable form of testosterone, a key androgen hormone responsible for regulating numerous physiological processes in both men and women. The Free Testosterone - Saliva test measures the amount of unbound testosterone in saliva, expressed in picograms per milliliter (pg/mL). Unlike total testosterone tests in blood, saliva testing specifically assesses the hormone’s biologically active fraction, which is readily available for use by the body’s tissues.

Although Testosterone is generally viewed as a male-only hormone, women’s ovaries also make small amounts of testosterone. It helps many organs and body processes in women. Free testosterone and albumin-bound testosterone are also referred to as bioavailable testosterone. This is the testosterone that is easily used by your body.

Although Testosterone is generally viewed as a male-only hormone, women’s ovaries also make small amounts of testosterone. It helps many organs and body processes in women. Free testosterone and albumin-bound testosterone are also referred to as bioavailable testosterone. This is the testosterone that is easily used by your body.

Thyroxine is a hormone produced by the thyroid gland. The term “free thyroxine” means the measured thyroxine that is not bound to proteins in the blood.

The free T4 index (FTI) is a blood test used to diagnose thyroid disorders. T4, also called thyroxine, is a thyroid hormone. The test measures how much of it is in your blood to help determine whether your thyroid gland is underactive (hypothyroidism) or overactive (hyperthyroidism).

Fructosamine is found in the plasma of both normal and diabetic individuals. “Fructosamine” is the term used to describe proteins that have been glycated (ie, are derivatives of the nonenzymatic reaction product of glucose and albumin). It has been advocated as an alternative test to hemoglobin A1c for the monitoring of long-term diabetic control. Fructosamine and hemoglobin A1c do not measure exactly the same thing, since fructosamine has a shorter half-life and appears to be more sensitive to short-term variations in glucose levels; however, this is not necessarily a disadvantage. Fructosamine is clearly superior in patients with abnormal hemoglobins because of the interference of abnormal hemoglobins in the anion-exchange chromatography methods for Hb A1c. Published reference interval for apparently healthy subjects between age 20 and 60 is 205−285 μmol/L and in a poorly-controlled diabetic population is 228−563 μmol/L with a mean of 396 μmol/L.

Emerging research seems to show a relationship between the rise in metabolic diseases and the increased consumption of fructose—particularly consumption of non-natural sources of fructose found in sugar-sweetened beverages and other processed foods.

Elevated fructose levels should be further investigated. Dietary fructose intake should be determined, modified if excessive, and monitored for metabolic changes.

Humans have a limited ability to metabolize fructose (fruit sugar). Fructose is metabolized differently from other sugars. A fructose load leads to accumulation of fructose-1-phosphate in cells which may partially deplete intracellular ATP levels in susceptible individuals.

Since fructose intolerance is a cellular event, rather than a single nutrient deficiency, symptoms may vary widely among persons. Preliminary evidence suggests clinical symptoms of fructose intolerance may include fatigue, headaches, weakness, dizziness, behavioral changes, and depressed immune function. Medical literature suggests that certain individuals with fructose intolerance may show hypertriglyceridemia, elevation of uric acid, and interference with copper metabolism.

Dietary sources of fructose are numerous; however, an excess intake of fructose should be avoided, rather than absolute removal of dietary fructose. In this manner, whole foods containing fructose (fruits and some vegetables) may be consumed, in order to benefit from their overall nutritional value.

Foods very rich in fructose include table sugar (sucrose), high fructose corn syrup, corn syrup, fruit juice concentrates and a large list of prepared foods containing sucrose and/or corn syrup. Reduction of excess dietary fructose intake by avoidance of foods very rich in fructose is suggested when fructose intolerance is exhibited.

The FT3 (Free Triiodothyronine) to Reverse T3 (rT3) ratio is a crucial biomarker for assessing thyroid function, particularly in the context of thyroid hormone metabolism and the body’s overall metabolic state. Triiodothyronine (T3) is the active form of thyroid hormone, essential for regulating metabolism, energy production, and numerous physiological processes. In contrast, Reverse T3 (rT3) is an inactive form produced when the body converts thyroxine (T4) into a metabolically inactive state. The FT3 to rT3 ratio provides insight into how effectively the body is converting T4 into its active form (T3) versus its inactive form (rT3), serving as an indicator of various health conditions and metabolic states.

Fumarate (together with Succinate and Malate) is used in the body’s metabolic pathway that generates cellular energy – the Citric Acid Cycle.

Fumarate (together with Succinate and Malate) is used in the body’s metabolic pathway that generates cellular energy – the Citric Acid Cycle. This cycle critically supports organ maintenance and neurological function. Fumarate is also a product of the urea cycle. Much like vitamin D, fumaric acid is formed by the body, in the skin, during exposure to sunlight.