HbA1c reflects average blood glucose exposure over roughly the past 3 months. It is one of the most stable markers of long-run glycemic load, and elevated HbA1c is associated with cardiovascular and microvascular risk in observational studies.

Fasting glucose captures a single-point snapshot of glucose regulation. Because it varies with sleep, stress, and time of last meal, it is best read together with HbA1c (which averages ~3 months of exposure).

Total testosterone measures both bound and free hormone. Because most testosterone is bound to SHBG, total T alone can be misleading — interpret alongside free testosterone and SHBG.

Free testosterone represents the bioactive fraction not bound to SHBG or albumin. Total T can look normal while free T is low if SHBG is high.

SHBG binds sex hormones and modulates their bioavailability. It also acts as a metabolic barometer — low SHBG tracks with insulin resistance and hepatic steatosis in cohort data.

TSH is a pituitary signal, not a thyroid hormone itself. It rises when the body senses insufficient thyroid hormone. Interpret alongside Free T3 and Free T4 — TSH alone can miss subclinical patterns.

Free T3 is the metabolically active thyroid hormone. Free T3 can look normal while symptoms persist — reverse T3 and cellular receptor sensitivity also matter but are rarely captured in routine panels.

Free T4 is the storage form of thyroid hormone; peripheral tissues convert it to active T3. Free T4 changes more slowly than Free T3, making it useful for trend tracking.

ApoB counts every atherogenic lipoprotein particle (LDL, IDL, VLDL remnants, Lp(a)). It is generally considered a more precise cardiovascular risk marker than LDL-C alone — particularly when LDL-C and ApoB disagree.

LDL-C estimates cholesterol carried by LDL particles. It is a simple, widely-available marker of atherogenic lipid burden but does not distinguish particle count from cholesterol content — ApoB does that better.

HDL-C reflects reverse cholesterol transport capacity, roughly. Low HDL-C is associated with CV risk in cohort studies, though trials that raised HDL-C pharmacologically did not reduce events — so it may be a risk marker, not a modifiable target.

hs-CRP is a general marker of systemic inflammation and modestly predicts cardiovascular events. It rises with acute infection, injury, obesity, and chronic inflammatory conditions — always retest before drawing conclusions from a single elevated value.

Hemoglobin carries oxygen from lungs to tissues. Both low and unusually high hemoglobin have implications: low points toward anemia (many causes); high can reflect dehydration, hypoxia, smoking, or a hematologic disorder.

Ferritin reflects stored iron but is also an acute-phase reactant — it rises with inflammation, infection, obesity, and liver disease. Interpretation requires context: hs-CRP, transferrin saturation, and clinical picture.

25-hydroxyvitamin D is the storage form of vitamin D and the standard blood measure. Below 20 ng/mL is widely considered deficient; the upper end of "optimal" is contested — large trials have not demonstrated clear benefit from supplementation once levels are sufficient.

IGF-1 mediates many of growth hormone’s effects and is linked to protein synthesis and cellular growth. Cohort data suggest a J-shaped mortality curve — both very low and very high IGF-1 are associated with worse outcomes, especially in older adults. Age-specific reference ranges matter.

Homocysteine is a methylation intermediate. Elevated levels are associated with cardiovascular and cognitive risk in cohort studies; trials lowering homocysteine with B-vitamins have shown modest stroke benefit but no consistent CV mortality benefit.