Evidence-Based Supplement & Herb Guides

Insulin Resistance Blood Test Panel: Fasting Insulin, Glucose, C-Peptide, HOMA-IR, and Results

Understand an insulin resistance panel with fasting insulin, glucose, C-peptide, and HOMA-IR, including result patterns, limits, preparation, and follow-up.

An insulin resistance blood test panel combines fasting insulin and glucose with calculated HOMA-IR and, in some panels, C-peptide. The tests show how much...

Insulin/C-Peptide Ratio Test: Exogenous Insulin Use, Insulin Production, and Results

Learn how the insulin/C-peptide molar ratio is calculated and interpreted during hypoglycemia, including exogenous insulin patterns, endogenous secretion, assay limits, and follow-up tests.

The insulin/C-peptide ratio is a calculated laboratory value used mainly during the investigation of documented hypoglycemia. Insulin and C-peptide are released together when the...

Leptin Blood Test: High, Low, Obesity, Metabolic Health, and Results

Understand what a leptin blood test measures, why levels may be high or low, how obesity and leptin resistance affect results, and when specialized follow-up is appropriate.

A leptin blood test measures a hormone made mainly by fat cells that helps the brain assess long-term energy stores. Leptin usually rises as...

Pancreatic Hormone Test Panel: Insulin, C-Peptide, Proinsulin, Glucagon, and Results

Learn how insulin, C-peptide, proinsulin, and glucagon are used in a pancreatic hormone test panel, what result patterns mean, and why timing and assay context matter.

A pancreatic hormone test panel measures selected hormones made by islet cells, commonly insulin, C-peptide, proinsulin, and glucagon. These tests can help investigate documented...

Pancreatic Polypeptide Test: High Levels, Pancreatic Function, and Results

Learn what a pancreatic polypeptide test measures, why levels may be high, how fasting and age affect results, and when tumor or vagal-function follow-up is appropriate.

A pancreatic polypeptide test measures a 36-amino-acid hormone released mainly by specialized cells in the pancreas. Pancreatic polypeptide rises after eating, during exercise, and...

Proinsulin Blood Test: High Levels, Insulin Production, and Results

Learn what a proinsulin blood test measures, why levels may be high, how results help evaluate insulin production and hypoglycemia, and when insulinoma follow-up is needed.

A proinsulin blood test measures the precursor molecule that pancreatic beta cells process into insulin and C-peptide. Healthy beta cells convert most proinsulin before...

Somatostatin Blood Test: High Levels, Pancreatic Hormone, and Results

Understand what a somatostatin blood test measures, why levels may be high, how somatostatinoma affects glucose and digestion, and what follow-up testing is needed.

A somatostatin blood test measures a hormone that acts as a broad inhibitor of endocrine and digestive activity. Somatostatin is produced by delta cells...

Vasoactive Intestinal Peptide (VIP) Test: High Levels, Diarrhea, and Results

Learn when a VIP blood test is used for high-volume watery diarrhea, how high results support VIPoma, and why potassium loss, specimen handling, and imaging matter.

A vasoactive intestinal peptide test measures VIP, a neuropeptide that relaxes smooth muscle and stimulates secretion of water and electrolytes into the intestine. The...

Androgen Deficiency Blood Test Panel: Testosterone, SHBG, LH, FSH, Symptoms, and Results

Understand an androgen deficiency blood test panel, including testosterone, SHBG, free testosterone, LH, FSH, result patterns, causes, preparation, and follow-up.

An androgen deficiency blood test panel looks beyond a single testosterone number. It combines total testosterone with sex hormone-binding globulin (SHBG), free or calculated...

Androstenedione Test in Men: High, Low, Adrenal, Testicular, and Results

Learn what an androstenedione test in men measures, why levels may be high or low, how adrenal and testicular sources are evaluated, and which follow-up tests help.

An androstenedione test measures a steroid hormone made by both the adrenal glands and testes. Androstenedione is weaker than testosterone, but it is an...

Anti-Mullerian Hormone (AMH) Test in Men: Testicular Function and Results

Understand AMH testing in men, including Sertoli-cell function, age-related ranges, low and high results, infertility and azoospermia uses, limitations, and follow-up tests.

An anti-Müllerian hormone (AMH) test in males mainly reflects Sertoli-cell activity in the testes. AMH is best known for its role in fetal male...

Bioavailable Testosterone Test: Low Levels, Normal Range, SHBG, and Results

Learn how bioavailable testosterone is measured, how SHBG changes results, what low levels may mean, when testing is useful, and which follow-up tests guide diagnosis.

A bioavailable testosterone test estimates the testosterone that is free or loosely bound to albumin and therefore more readily available to tissues. It excludes...

DHEA-S Test in Men: High, Low, Adrenal Androgens, and Results

Learn what a DHEA-S test in men measures, why levels may be high or low, how age and supplements affect results, and which adrenal tests guide follow-up.

A DHEA-S test measures dehydroepiandrosterone sulfate, the most abundant circulating adrenal androgen. In men, DHEA-S comes almost entirely from the adrenal glands, making it...

Dihydrotestosterone (DHT) Test: High, Low, Hair Loss, Prostate, and Results

Understand DHT testing, including high and low results, 5-alpha-reductase inhibitors, hair loss, prostate effects, assay limitations, and appropriate follow-up.

A dihydrotestosterone (DHT) test measures a potent androgen made when the enzyme 5-alpha-reductase converts testosterone into DHT. The hormone is essential for fetal development...

Estradiol (E2) Test in Men: High, Low, Normal Range, and Hormone Balance

Understand estradiol testing in men, including sensitive assays, high and low causes, testosterone and SHBG patterns, gynecomastia, bone health, and follow-up.

An estradiol (E2) test in men measures the most biologically active form of estrogen. Most male estradiol is created when aromatase converts testosterone into...

Follicle-Stimulating Hormone (FSH) Test in Men: Sperm Production, Fertility, and Results

Understand the FSH test in men, including high, low, and normal results, sperm-production patterns, infertility causes, related hormones, and next steps.

A follicle-stimulating hormone (FSH) test in men helps assess pituitary signaling to the sperm-producing tissue of the testes. FSH acts on Sertoli cells, which...

Free Testosterone Test: Low Levels, Normal Range, SHBG, Symptoms, and Results

Understand when a free testosterone test is useful, how SHBG and test method affect results, what low or high levels may mean, and which follow-up tests help confirm the cause.

A free testosterone test estimates the small share of testosterone that is not tightly bound to sex hormone-binding globulin (SHBG). It can clarify hormone...

Gynecomastia Hormone Test Panel: Testosterone, Estradiol, LH, hCG, Prolactin, and Results

Learn what a gynecomastia hormone panel measures, how testosterone, estradiol, LH, hCG, and prolactin patterns are interpreted, and when imaging or urgent assessment is needed.

A gynecomastia hormone test panel helps investigate true glandular breast enlargement in a male, especially when it begins suddenly, is painful, occurs before or...

Hypogonadism Blood Test Panel: Total Testosterone, Free Testosterone, LH, FSH, Prolactin, and Results

Understand how a hypogonadism blood test panel uses total and free testosterone, LH, FSH, and prolactin to confirm low testosterone, identify its cause, and guide safe treatment.

A hypogonadism blood test panel checks whether a man has consistently low testosterone and helps locate the cause in the testes, pituitary, hypothalamus, hormone-binding...

Inhibin B Test in Men: Sperm Production, Testicular Function, and Results

Understand what an inhibin B test shows about Sertoli-cell and sperm-producing function, how low or normal results relate to FSH and semen analysis, and why it cannot predict fertility alone.

An inhibin B test measures a hormone made mainly by Sertoli cells in the testes and provides indirect information about seminiferous tubule activity and...