Blood Markers & Labs
Laboratory values, biomarkers, diagnostic tests, and their interpretation
7 insights across 3 sources
#351 ‒ Male fertility: optimizing reproductive health, diagnosing and treating infertility, and navigating testosterone replacement therapy
Evaluation of male infertility follows a stepwise approach: 1) history and physical exam, 2) semen analysis to document azoospermia or oligospermia, and 3) hormonal testing (eg, pituitary and gonadal hormones) to distinguish primary testicular failure from secondary hypothalamic‑pituitary causes, because spermatogenesis is regulated by the brain via the hypothalamic–pituitary–testicular axis with negative feedback.
Hormonal evaluation helps determine whether absent sperm production is due to intrinsic testicular failure (primary) or lack of central stimulation (secondary).
A standard semen analysis reports multiple distinct parameters—ejaculate volume, sperm concentration (number per mL), motility (percent moving and quality of forward progression), morphology (shape), and semen fluid properties (liquefaction time, agglutination/clumping, viscosity)—because each provides different information about male reproductive function.
Round cells (described separately) and fluid characteristics are part of a full analysis, not just count and motility.
Semen analysis should be interpreted as a composite profile—patterns across parameters matter more than any single nonzero abnormality; except for azoospermia (zero sperm), individual abnormal values often do not reliably predict fertility on their own.
Think of the analysis like a 'poker hand'—the combination and severity of abnormal parameters guide diagnosis and management.
The presence of 'round cells' on semen analysis (usually reported numerically) represents either leukocytes (suggesting infection/inflammation) or immature germ cells; a commonly used threshold is fewer than 1,000,000 round cells (per ejaculate or per mL depending on lab) as within normal limits.
High numbers of round cells prompt further evaluation for infection or abnormal spermatogenesis; verify whether the lab reports per mL or per ejaculate when applying the numeric threshold.
Accurately measuring free-living food intake is a major unresolved barrier in nutrition science; substantially better objective intake measurement would materially improve causal inference and the validity of dietary research.
Limitations of current dietary assessment approaches in free-living populations and the transformative potential of improved measurement.
A concise clinical assessment framework uses DEXA body composition and targeted blood tests to answer three questions quickly: (1) Is the person over- or under-nourished (energy balance/fat amount)? (2) Are they adequately muscled or under-muscled (lean mass)? (3) Are they metabolically healthy (glucose disposal and metabolic biomarkers)? Answers guide whether to increase, decrease, or maintain calories, set protein targets, and prioritize types of exercise.
DEXA provides subcutaneous vs visceral fat and lean-mass data; metabolic bloodwork evaluates glucose disposal and related metabolic health.
Fat distribution (visceral vs subcutaneous) and metabolic health are more informative than total body weight alone when deciding energy prescription; clinically, many people present slightly over-nourished and may benefit from modest reductions in energy intake rather than aggressive or complex dietary changes.
Emphasizes evaluating where fat is stored and metabolic markers rather than relying solely on weight or BMI.