The words on your lab report, defined
52 terms in plain English: what each one means, why it matters after 45, and which page on this site covers what to do about it.
What the lines on a blood panel are measuring.
ApoB
Apolipoprotein BApoB is the protein carried on each LDL and related cholesterol particle, so its blood level is a count of the particles that build arterial plaque.
Cortisol
The stress hormoneCortisol is a hormone made by the adrenal glands that helps the body respond to stress and regulates blood sugar, blood pressure and inflammation.
DHEA-S
DHEA sulfateDHEA-S (dehydroepiandrosterone sulfate) is an adrenal hormone the body converts into testosterone and estrogen; levels fall steadily with age.
Estradiol
E2Estradiol (E2) is the most potent form of estrogen and the main one before menopause; a blood test measures it in both women and men.
Fasting insulin
Fasting serum insulinFasting insulin is the level of insulin in the blood after an overnight fast, showing how hard the pancreas is working to keep glucose in range.
Ferritin
Serum ferritinFerritin is the protein that stores iron in the body, and its blood level is the main test of how much iron you have in reserve.
Free T3
Free triiodothyronineFree T3 is the unbound, active form of triiodothyronine, the thyroid hormone that enters tissues and sets how the body uses energy.
Free T4
Free thyroxineFree T4 is the unbound portion of thyroxine, the main hormone the thyroid makes, measured alongside TSH to check thyroid function.
Free testosterone
Free TFree testosterone is the small share of testosterone in the blood that is not bound to proteins, so it is available to act on your tissues.
FSH
Follicle-stimulating hormoneFSH (follicle-stimulating hormone) is a pituitary hormone that drives egg development in women and sperm production in men.
HbA1c
A1cHbA1c is a blood test showing average blood glucose over the past two to three months, used to screen for and monitor prediabetes and diabetes.
Hematocrit
HCTHematocrit is the share of your blood made up of red blood cells, measured on a routine blood count and watched closely on testosterone therapy.
HOMA-IR
Homeostatic model assessment of insulin resistanceHOMA-IR is a score calculated from fasting insulin and fasting glucose that estimates how resistant the body is to insulin.
Homocysteine
Total homocysteineHomocysteine is an amino acid that B12, B6 and folate break down; a high blood level can signal a B-vitamin shortfall and is linked to heart risk.
hs-CRP
High-sensitivity C-reactive proteinhs-CRP is a sensitive blood test for C-reactive protein, an inflammation marker made by the liver, used to help estimate heart disease risk.
IGF-1
Insulin-like growth factor 1IGF-1 (insulin-like growth factor 1) is a hormone that carries out many effects of growth hormone and is the steadier marker used to track it.
LH
Luteinizing hormoneLH (luteinizing hormone) is a pituitary hormone that tells the testicles to make testosterone and triggers ovulation in women.
Lipoprotein(a)
Lp(a)Lipoprotein(a) is an LDL-like cholesterol particle whose level is set mainly by genes, and a high level raises the risk of heart disease and stroke.
Prolactin
PRLProlactin is a pituitary hormone best known for milk production; a raised level can lower testosterone, sex drive and fertility.
PSA
Prostate-specific antigenPSA (prostate-specific antigen) is a protein made by the prostate; a blood test for it is used in prostate screening and testosterone monitoring.
SHBG
Sex hormone-binding globulinSHBG is a liver protein that binds testosterone and estrogen in the blood, which decides how much of each hormone is free for your tissues to use.
Total testosterone
Serum testosteroneTotal testosterone is a blood test measuring all the testosterone in circulation, both the part bound to proteins and the small free part.
TSH
Thyroid-stimulating hormoneTSH is a pituitary hormone that tells the thyroid how much hormone to make, so its blood level is the usual first check of thyroid function.
Vitamin D (25-hydroxyvitamin D)
25(OH)DA vitamin D test usually measures 25-hydroxyvitamin D, the storage form the liver makes, to judge whether the body has enough vitamin D.
The hormones and changes that shape health after 45.
Andropause
Male menopauseAndropause is a popular name for the gradual fall in testosterone as men age; clinicians more often use the term late-onset hypogonadism.
Aromatization
Aromatase activityAromatization is the conversion of androgens such as testosterone into estrogens by the enzyme aromatase, which in men happens mostly in body fat.
Estrogen
EstradiolEstrogen is a group of sex hormones, chiefly estradiol, estrone and estriol, that governs female reproductive health and also acts on bone in both sexes.
Genitourinary syndrome of menopause
GSMGenitourinary syndrome of menopause (GSM) is the set of vaginal, urinary and sexual symptoms caused by low estrogen; it was once called vaginal atrophy.
Hypogonadism
Low testosteroneHypogonadism is when the sex glands, the testes or ovaries, make little or no sex hormone, either from a gland problem or a pituitary signal problem.
Insulin resistance
Impaired insulin sensitivityInsulin resistance is when muscle, fat and liver cells stop responding well to insulin, so the pancreas makes more of it to keep blood sugar in check.
Progesterone
P4Progesterone is a hormone made mainly by the ovaries that prepares the lining of the uterus each month and helps sustain early pregnancy.
Sarcopenia
Age-related muscle lossSarcopenia is the gradual, age-related loss of muscle mass, strength and physical function that can make everyday tasks harder and raise the risk of falls.
Testosterone
TTestosterone is a sex hormone made by the testicles and ovaries that supports sex drive, muscle, bone and red blood cell production in men and women.
Vasomotor symptoms
VMSVasomotor symptoms are hot flashes and night sweats, sudden waves of heat, sweating and flushing caused by changes in how blood vessels widen and narrow.
The families medicines belong to, and what sets each apart.
5-alpha-reductase inhibitor
5-ARIA 5-alpha-reductase inhibitor is a medicine that blocks the enzyme that turns testosterone into DHT, a more potent male hormone.
Aromatase inhibitor
AIAn aromatase inhibitor is a medicine that blocks aromatase, the enzyme that turns androgens such as testosterone into estrogen, lowering estrogen levels.
Bioidentical hormones
BHRTBioidentical hormones are lab-made hormones with the same chemical structure as those the body makes, available as FDA-approved and compounded products.
GHRH analog
Growth hormone-releasing hormone analogA GHRH analog is a lab-made version of growth hormone-releasing hormone that prompts the pituitary to release the body's own growth hormone.
GIP/GLP-1 dual agonist
Dual incretin agonistA GIP/GLP-1 dual agonist is a medicine that activates the receptors for two gut hormones, GIP and GLP-1, rather than GLP-1 alone.
GLP-1 receptor agonist
GLP-1 agonistA GLP-1 receptor agonist is a medicine that copies the gut hormone GLP-1, helping release insulin when blood sugar is high and slowing stomach emptying.
PDE5 inhibitor
Phosphodiesterase type 5 inhibitorA PDE5 inhibitor is a medicine that blocks the enzyme phosphodiesterase type 5, increasing blood flow to the penis during sexual stimulation.
SERM
Selective estrogen receptor modulatorA SERM is a medicine that acts on estrogen receptors, behaving like estrogen in some tissues and blocking it in others.
The terms in the fine print: approval, compounding, coverage.
503A pharmacy
503A compounding pharmacyA 503A pharmacy is a state-licensed pharmacy that compounds medications under section 503A of federal law, on prescriptions for individual patients.
503B outsourcing facility
Outsourcing facilityA 503B outsourcing facility is an FDA-registered compounder of sterile drugs that must follow manufacturing-quality rules and is inspected by the FDA.
Compounded medication
Compounded drugA compounded medication is one a licensed pharmacy prepares for an individual patient by mixing or altering ingredients. It is not FDA-approved.
FDA-approved
FDA approvalFDA-approved means the FDA has reviewed a drug's evidence and decided its benefits outweigh its risks for a specific intended use.
FDA-cleared
510(k) clearanceFDA-cleared means the FDA let a medical device be sold because it is substantially equivalent to one already on the market. It is not FDA approval.
Lab-developed test
Laboratory-developed testA lab-developed test is a diagnostic test designed, made and run within a single laboratory, rather than a kit sold to many labs.
Letter of medical necessity
LMNA letter of medical necessity is a clinician's written statement that an item or service is needed to diagnose or treat a specific condition.
Off-label use
Off-label prescribingOff-label use is prescribing an FDA-approved drug for a condition, dose, form or group of patients that its approved labeling does not cover.
Prior authorization
PreauthorizationPrior authorization is approval a health plan may require before you get a service or fill a prescription, as a condition of the plan covering it.
Reference range
Reference intervalA reference range is the span of results a lab reports as normal for a test, based on results from a large group of healthy people.
Definitions are educational and are not medical advice. For questions about cost, eligibility and care, see the FAQ.