lab-guides

Selenium cofactors thyroid T4→T3 conversion and glutathione synthesis. Soil-driven deficiency is common. Two Brazil nuts a day covers the daily requirement for most adults.

IGF-1 mediates growth hormone action — too low tracks with frailty; too high associates with cancer risk in cohort data. The optimal range is narrow and age-dependent.

Gamma-glutamyl transferase is the most sensitive marker for alcohol-related liver stress — it rises before ALT/AST and falls within weeks of reducing intake. Optimal below 30 U/L.

SHBG determines how much of your testosterone and estradiol is biologically active. Low SHBG often signals insulin resistance; high SHBG can mask low free testosterone even when total testosterone appears normal.

Zinc is a trace mineral cofactor for immune response, testosterone synthesis, and wound healing. Serum levels below 60 µg/dL indicate clinically significant deficiency — common in older adults, vegans, and heavy exercisers.

Morning cortisol (7–9 a.m.) reflects the cortisol awakening response — the healthy surge that primes alertness. Optimal 12–18 µg/dL. Values outside this window signal sleep debt, overtraining, or HPA axis dysregulation worth investigating.

Elevated uric acid raises gout, kidney-stone, and hypertension risk and tracks with metabolic syndrome. Optimal is the lower half of the reference range — primary drivers are fructose and alcohol.

Homocysteine accumulates when B-vitamin methylation pathways are sluggish. Elevated values track with cardiovascular and cognitive-decline risk — and are often correctable with dietary folate, B12, and B6.

Total testosterone measures bound + unbound hormone; free testosterone is the bioactive fraction. Symptoms of low T correlate better with free T than with total — order both, and always draw blood at 7–10 a.m.

The omega-3 index measures EPA + DHA as a percentage of total fatty acids in red blood cell membranes. Strong inverse association with cardiovascular mortality. Target 8–12%; most Western adults sit at 4–6%.

Lipoprotein(a) is a genetically fixed atherogenic particle — lifestyle changes cannot lower it. Elevated Lp(a) raises cardiovascular and aortic-valve risk independent of LDL. Test once; if elevated, tighten everything else.

The standard lipid panel measures the main circulating fats. LDL-C is the classic risk marker, but triglycerides and HDL contextualise it — and the TG/HDL ratio is a strong insulin-resistance proxy.