Health Metrics Encyclopedia
Every biometric, cycle signal, hormone, and symptom Go Go Gaia tracks, defined in one place and sourced to real research. Each entry explains what a metric measures and how it's measured, not what your own number means.
Educational reference content, not medical advice. Entries describe what the research shows at a population level. For questions about your own results, please consult your doctor.
Biometrics & Vitals
- HRV (Heart Rate Variability) The variation in time between heartbeats, tracked overnight as a signal of autonomic nervous system balance.
- Resting Heart Rate Beats per minute at rest, typically measured overnight or first thing in the morning.
- Basal Body Temperature Body temperature at rest, taken immediately on waking, used to spot the post-ovulation temperature shift.
- HRV: RMSSD The specific HRV calculation most consumer wearables report.
- Heart Rate Beats per minute, measured continuously or on demand.
- Wrist Temperature Skin temperature sampled at the wrist overnight by devices like Apple Watch.
- Blood Pressure The force of blood against artery walls, recorded as systolic over diastolic.
- Respiratory Rate Breaths per minute at rest, tracked overnight by many wearables.
- SpO2 (Blood Oxygen Saturation) The percentage of oxygen-saturated hemoglobin in the blood.
- VO2 Max An estimate of the maximum rate of oxygen your body can use during exercise.
- Blood Glucose The concentration of sugar in the blood, measured via fingerstick or continuous glucose monitor.
- Sleep Stages REM, deep, and core sleep as estimated by wearable sensors overnight.
- Sleep Latency How long it takes to fall asleep after getting into bed.
- Body Temperature Core body temperature, distinct from basal or skin temperature readings.
- Active Energy Calories burned through movement above resting baseline.
- Step Count Steps taken per day, counted by an accelerometer in a phone, watch, or fitness tracker.
- Time in Daylight The daily time an Apple Watch's ambient light sensor detects light bright enough to count as daylight, distinct from indoor lighting.
- Audio Exposure Headphone and environmental sound levels an iPhone or Apple Watch logs in decibels, covering both connected-headphone loudness and ambient noise.
Body Composition & Fitness
- BMI (Body Mass Index) A person's weight in kilograms divided by height in meters squared, a population-level measure that correlates with body fat but doesn't measure it directly.
- Body Fat Percentage The share of total body weight made up of fat tissue, estimated with methods from DEXA scans to at-home bioelectrical impedance scales.
- Bone Density The amount of mineral packed into a given area of bone, most commonly measured with a DEXA scan.
- Cardio Recovery (Heart Rate Recovery) How much a person's heart rate falls in the minute right after exercise stops, estimated automatically by Apple Watch from workout heart-rate data.
- Exercise Minutes Apple's per-day tally of time spent moving at or above brisk-walking intensity, based on Watch sensor data. It syncs from Apple Health alongside stand time as part of the Activity rings.
- Flights Climbed The number of floors ascended, counted by the barometer built into iPhone and Apple Watch. Apple Health syncs it as a daily activity metric alongside step count.
- Grip Strength The force a person can produce with their hand and forearm muscles when squeezing, measured with a handheld dynamometer.
- Lean Body Mass Total body weight minus fat mass, covering muscle, bone, organs, and water, measured with the same tools used to estimate body fat percentage.
- Visceral Fat Fat stored deep in the abdominal cavity around organs like the liver and intestines, distinct from subcutaneous fat just under the skin.
- Waist Circumference A tape-measure reading taken around the abdomen using a standardized protocol, tracked as an anthropometric marker of central body size.
- Walking Speed & Gait Metrics A family of motion-sensor measurements, including walking speed, step length, asymmetry, and steadiness, that iPhone and Apple Watch estimate during everyday walking.
Cycle & Fertility
- Cervical Mucus Vaginal discharge that changes texture across the cycle and is used as a fertility-awareness sign.
- LH Surge The rapid rise in luteinizing hormone that triggers ovulation.
- Luteal Phase The second half of the cycle, from ovulation to the next period.
- Follicular Phase The first half of the cycle, from the start of the period to ovulation.
- Cervical Position Changes in cervix height, softness, and openness across the cycle.
- Ovulation Test (OPK) A urine test strip that detects the LH surge ahead of ovulation.
- Period Flow The volume and pattern of menstrual bleeding, typically logged by intensity.
- Ovulation The release of an egg from the ovary, roughly midway through a typical cycle.
- Menstrual Phase The days of active bleeding at the start of the cycle.
- Fertile Window The days in a cycle when pregnancy is biologically possible.
- Cycle Length The number of days from the first day of one period to the first day of the next.
- Spotting / Intermenstrual Bleeding Light bleeding that occurs outside the expected period.
- Anovulatory Cycle A cycle in which no egg is released.
Pregnancy & IVF
- Fetal Heart Rate The fetal heartbeat rate measured by Doppler or ultrasound at prenatal visits, logged from appointments.
- Fundal Height The tape measurement from pubic bone to the top of the uterus, recorded at prenatal checkups.
- Antral Follicle Count The number of small ovarian follicles counted on early-cycle ultrasound, an ovarian-reserve marker alongside AMH.
- Endometrial Thickness The ultrasound measurement of the uterine lining, tracked in IVF and embryo-transfer cycles.
- Embryo Grading The lab notation describing an embryo's appearance at day 3 or day 5, as reported by an IVF clinic.
- IVF Cycle Numbers The counts recorded through an IVF cycle: eggs retrieved, mature, fertilized, and embryos developing.
- Semen Analysis A laboratory evaluation of sperm count, motility, and morphology, assessed with methods standardized in the WHO laboratory manual.
- Sperm DNA Fragmentation (DFI) Single- and double-strand breaks in the DNA packaged inside a sperm's nucleus, reported as the DNA Fragmentation Index.
Hormones & Labs
- AMH (Anti-Müllerian Hormone) A hormone produced by ovarian follicles, commonly used as a marker of ovarian reserve.
- Estradiol The primary form of estrogen during reproductive years, rising and falling across the cycle.
- TSH (Thyroid-Stimulating Hormone) A pituitary hormone that signals the thyroid gland to produce thyroid hormone.
- Ferritin A protein that stores iron, used as a lab marker of the body's iron reserves.
- Estrone (E1) A weaker form of estrogen, more prominent after menopause.
- Progesterone The hormone that rises after ovulation and supports the luteal phase.
- FSH (Follicle-Stimulating Hormone) The pituitary hormone that stimulates follicle growth in the ovary.
- Testosterone An androgen hormone present in smaller amounts in women, involved in libido and muscle maintenance.
- Free Testosterone The portion of testosterone not bound to carrier proteins, considered biologically active.
- SHBG (Sex Hormone-Binding Globulin) A protein that binds sex hormones in the blood, affecting how much is free and active.
- DHEA-S An adrenal androgen used as a marker of adrenal hormone production.
- Prolactin A pituitary hormone best known for its role in milk production.
- Cortisol The primary stress hormone, produced by the adrenal glands on a daily rhythm.
- Insulin The hormone that regulates blood sugar by moving glucose into cells.
- Free T4 (Free Thyroxine) The unbound, biologically active portion of thyroxine, the thyroid gland's main secreted hormone.
- Free T3 (Free Triiodothyronine) The small unbound fraction of T3, the biologically active thyroid hormone, circulating in blood.
- Reverse T3 (rT3) An inactive form of thyroid hormone produced when deiodinase enzymes break down T4.
- Thyroid Antibodies (TPO & Thyroglobulin Antibodies) Immune proteins that target parts of the thyroid gland, used as markers of thyroid autoimmunity.
- hCG (Human Chorionic Gonadotropin) A hormone made by the developing placenta and detected by pregnancy tests.
- PdG (Pregnanediol Glucuronide) The urinary metabolite of progesterone, used to confirm ovulation without a blood draw.
- E3G (Estrone-3-Glucuronide) A urinary breakdown product of estradiol, read by at-home fertility monitors to track the estrogen curve.
- 17-OH Progesterone (17-Hydroxyprogesterone) A steroid hormone made as an in-between step on the pathway from progesterone toward cortisol.
- Androstenedione An androgen produced by the ovaries and adrenal glands that serves as a precursor to testosterone and estrone.
- Urinalysis The standard urine test, done three ways: a visual color check, a chemical dipstick, and a microscope exam.
- Urine Hormone Metabolites Urinary cortisol, melatonin's breakdown product aMT6s, and the DNA-oxidation marker 8-OHdG.
- Saliva Hormone Testing Measuring a hormone in a saliva sample instead of blood; salivary cortisol has real clinical backing, but salivary sex-hormone panels don't.
Metabolic, Kidney & Liver Labs
- Fasting Glucose Blood glucose measured after at least eight hours without food, a baseline reading on standard metabolic panels.
- HbA1c (Hemoglobin A1c) The share of hemoglobin with glucose attached, reflecting average blood glucose over roughly three months.
- C-Peptide A protein chain the pancreas releases alongside insulin in equal amounts, measured by lab blood draw.
- Creatinine A muscle waste product filtered by the kidneys, a standard part of routine bloodwork and kidney function estimates.
- BUN (Blood Urea Nitrogen) The amount of urea nitrogen in the blood, a liver-made waste product filtered out by the kidneys.
- eGFR (Estimated Glomerular Filtration Rate) A calculated estimate of how fast the kidneys filter blood, derived from creatinine plus age and sex.
- ALT (Alanine Aminotransferase) A liver enzyme that leaks into the blood when liver cells are stressed or damaged.
- AST (Aspartate Aminotransferase) An enzyme found in the liver, heart, muscle, kidneys, and red blood cells, released when those cells are damaged.
- Alkaline Phosphatase (ALP) An enzyme made mainly in the liver and bone, measured as part of a liver or metabolic panel.
- Bilirubin (Total & Direct) A pigment made when the body breaks down heme from retired red blood cells, reported as total and direct fractions.
- Direct (Conjugated) Bilirubin The water-soluble, liver-processed fraction of bilirubin, reported alongside total bilirubin on liver panels.
- Sodium (Serum) The major electrolyte in the fluid outside cells, regulated by the kidneys to help set blood volume, and also logged as a dietary nutrient.
- Potassium (Serum) The body's main intracellular electrolyte, essential for nerve signaling and muscle contraction, and also logged as a dietary nutrient.
- Chloride The major anion in the fluid outside cells, moving alongside sodium to help set fluid balance.
- Bicarbonate (CO2) The main chemical buffer in blood, resisting shifts in pH, reported as total CO2 on a metabolic panel.
- Calcium (Serum) The body's most abundant mineral, mostly stored in bone, with blood levels regulated by parathyroid hormone, vitamin D, and calcitonin.
- Magnesium (Serum) A mineral cofactor in more than 300 enzyme reactions, mostly stored in bone and soft tissue rather than blood.
- Phosphorus (Serum) The body's second most abundant mineral, mostly stored in bone alongside calcium, with the rest forming part of ATP, DNA, and RNA.
- Uric Acid The final breakdown product of purines, made mostly in the liver and cleared by the kidneys.
- Albumin The most abundant protein in blood plasma, made by the liver to hold fluid in vessels and carry substances through the body.
- Total Protein A blood test that adds up every protein circulating in plasma, mainly albumin and a family of proteins called globulins.
- GGT (Gamma-Glutamyl Transferase) A liver-concentrated enzyme that helps recycle the antioxidant glutathione, used to help interpret an elevated alkaline phosphatase result.
Lipids & Heart Health Labs
- Total Cholesterol The combined amount of cholesterol in the blood, counting the cholesterol carried by every type of lipoprotein particle, including HDL, LDL, and VLDL.
- HDL Cholesterol The cholesterol carried inside high-density lipoprotein particles, the smallest and densest of the lipoprotein particles that move fats through the bloodstream.
- LDL Cholesterol The cholesterol carried by low-density lipoprotein, the particle that delivers most of the cholesterol circulating in blood to tissues around the body.
- Triglycerides A fat molecule built from one glycerol backbone joined to three fatty acids, the body's main form of stored and transported fat.
- ApoB (Apolipoprotein B) The main structural protein of LDL, VLDL, and related lipoprotein particles, with one ApoB molecule on each particle.
- Lipoprotein(a) A cholesterol-carrying particle built like an LDL particle with an extra protein, apolipoprotein(a), bonded to its surface.
- VLDL Cholesterol The triglyceride-carrying lipoprotein particle, usually calculated from the triglyceride value on a standard lipid panel rather than measured directly.
Blood Count (CBC)
- Hemoglobin The iron-containing protein inside red blood cells that picks up oxygen in the lungs and carries it to the rest of the body.
- Hematocrit The fraction of blood volume taken up by red blood cells, reported as a percentage.
- Red Blood Cell (RBC) Count The number of red blood cells, the body's oxygen-carrying cells, in a set volume of blood.
- White Blood Cell (WBC) Count The number of white blood cells, the cells of the immune system, in a set volume of blood.
- Platelet Count The number of platelets, the small cell fragments that clump to stop bleeding, in a set volume of blood.
- MCV (Mean Corpuscular Volume) The average size of red blood cells, one of the red cell indices reported as part of a complete blood count.
- MCH & MCHC The average hemoglobin mass (MCH) and average hemoglobin concentration (MCHC) per red blood cell, reported on a CBC alongside MCV.
Iron, Inflammation & Nutrients
- Serum Iron The iron circulating in blood, bound to the carrier protein transferrin, measured by blood draw.
- TIBC & Transferrin Saturation How much iron the blood's transferrin can carry (TIBC) and the share of that capacity currently in use.
- hs-CRP (High-Sensitivity C-Reactive Protein) A high-sensitivity blood test for C-reactive protein, a liver-made marker of inflammation.
- CRP (standard) The standard C-reactive protein assay used in general medical testing, distinct from the more sensitive hs-CRP assay above.
- ESR (Erythrocyte Sedimentation Rate) How far red blood cells settle in a tube of blood over one hour, an older marker of inflammation.
- Homocysteine An amino acid produced during methionine metabolism, kept in check by B12, folate, and B6.
- Vitamin D (25-Hydroxyvitamin D) The standard blood test for vitamin D status, measuring the storage form circulating in blood.
- Vitamin B12 A cobalt-containing vitamin the body needs for DNA synthesis and red blood cell formation.
- Folate (Vitamin B9) The B vitamin behind DNA synthesis and new cell formation.
- Vitamin A (Retinol) A fat-soluble vitamin measured on lab panels as serum retinol.
- Zinc An essential trace mineral behind hundreds of enzymes, with no dedicated body store.
- Iodine The trace element the thyroid uses to build T4 and T3, most often assessed through urine rather than blood.
Nutrition & Diet
- B Vitamins Thiamin, riboflavin, niacin, pantothenic acid, and biotin, five coenzyme vitamins tracked as a group (B6, B12, and folate have their own pages).
- Caffeine A central nervous system stimulant found in coffee, tea, and cacao, tracked in milligrams from logged meals and drinks.
- Calories (Dietary Energy) The kilocalories your food logger calculates from every meal you log, built from per-gram factors for protein, carb, fat, and alcohol.
- Carbohydrates A macronutrient that breaks down mostly into glucose, the body's main energy source, tracked in grams from logged meals.
- Copper A trace mineral required for enzymes involved in aerobic metabolism, connective tissue, and iron transport.
- Dietary Fat A macronutrient split into total, saturated, mono- and polyunsaturated, and trans fat plus dietary cholesterol, each tracked separately.
- Fiber A non-digestible carbohydrate that comes in soluble and insoluble forms, tracked in grams from logged meals.
- Omega-3 & Omega-6 Fatty Acids Two families of essential polyunsaturated fat, including ALA, EPA, DHA, and linoleic acid, tracked separately from logged food.
- Protein (Dietary) A macronutrient built from amino acids the body uses to build and repair tissue and make hormones, tracked in grams from logged meals.
- Selenium A trace mineral built into selenoproteins that activate thyroid hormone and support antioxidant defense.
- Sugar & Added Sugar Total sugar in a food and the added-sugar amount put in during processing, both tracked in grams from logged meals.
- Trace Minerals (Manganese, Chromium & Molybdenum) Manganese, chromium, and molybdenum, three trace minerals the body needs in very small amounts.
- Vitamin B6 A vitamin converted into the coenzyme PLP, used in amino acid metabolism and neurotransmitter synthesis.
- Vitamin C A water-soluble antioxidant vitamin involved in collagen synthesis and iron absorption, tracked from logged food.
- Vitamin E A fat-soluble antioxidant vitamin, made only by plants, that protects cell membranes from damage.
- Vitamin K A fat-soluble vitamin required to activate clotting factors, with a role in bone and vascular health.
- Water Intake The volume of fluid from drinks and water-rich foods logged over a day, a dietary total rather than a lab value or sensor reading.
Symptoms
- Hot Flashes A sudden wave of heat across the face, neck, and chest, often with sweating, most common during the menopause transition.
- Night Sweats Episodes of heavy sweating during sleep, sharing the same physiology as hot flashes.
- Hirsutism Coarse, pigmented hair growth in areas where growth depends on androgens, such as the face and chest.
- Hormonal Acne Acne that tracks with hormone shifts, driven by androgen receptors in sebaceous glands.
- Hair Thinning A drop in visible hair density on the scalp as fewer follicles grow at once.
- Bloating A feeling of abdominal fullness or swelling that shifts across the menstrual cycle.
- Breast Tenderness Soreness or heaviness in breast tissue that often builds during the luteal phase.
- Cramps (Dysmenorrhea) Crampy lower-abdominal pain around the start of a period, driven by prostaglandins that make the uterus contract.
- Fatigue A feeling of tiredness or low energy that doesn't fully lift with rest.
- Mood Swings Noticeable shifts in emotional state over hours or days, logged as a subjective symptom.
- Libido / Sex Drive Overall level of sexual desire, shaped by hormones, stress, sleep, and life context.
- Nausea A queasy, unsettled stomach sensation that can precede vomiting.
- Headache / Migraine Head pain that, for many, clusters in the days just before and during menstruation.
- Insomnia Difficulty falling asleep, staying asleep, or getting sleep that feels restful.
- Heart Palpitations The felt awareness of your own heartbeat, described as fast, fluttering, or pounding.
- Cold Intolerance An unusual sensitivity to cold, feeling cold when others are comfortable.
- Restless Legs An urge to move the legs at rest, often easing with movement.
- Discharge Vaginal fluid whose amount and texture shift across the menstrual cycle.
- Mindful Minutes Time logged in meditation or breathing sessions, synced from Apple Health.
- Brain Fog Fuzzy thinking, word-finding trouble, and forgetfulness that can show up across the menstrual cycle and, more consistently, during the menopause transition.
- Cycle-Related Digestive Changes Shifts in bowel habits and gut symptoms, such as looser stools, bloating, or constipation, that cluster in the days before and during a period.
- Cyclical Anxiety Worry, tension, or feeling on edge that follows a repeating pattern across the menstrual cycle, often heavier before a period.
- Cyclical Joint Pain Aching, stiffness, or soreness in the joints that varies with hormonal changes across the cycle or the menopause transition.
- Cyclical Low Back Pain Lower-back pain that shows up in a pattern tied to the menstrual cycle, most often right before or during a period.
- Dizziness & Lightheadedness A group of sensations, from feeling faint to a spinning feeling in the room, most often reflecting a temporary change in blood flow or balance signals.
- Food Cravings A strong urge to eat a specific food, often sweet, salty, or high in carbohydrates, that feels harder to ignore than general hunger.
- Heavy Menstrual Bleeding Menstrual blood loss experienced as excessive enough to interfere with physical, social, emotional, or daily life.
- Irregular Periods A pattern where the number of days between periods changes noticeably from one cycle to the next.
- Missed Period The absence of expected menstrual bleeding, judged against a person's own typical cycle length and timing.
- Ovulation Pain (Mittelschmerz) One-sided lower abdominal pain that shows up around the middle of the menstrual cycle, on the same side as that cycle's developing follicle.
- Pelvic Pain Discomfort felt in the lower abdomen, below the belly button, or in the pelvis and lower back.
- Vaginal Dryness A reduction in the vagina's natural moisture, often felt as itching, irritation, or discomfort during sex.
- Appetite Changes Shifts in hunger and eating compared to a person's usual pattern, with research showing a dip around ovulation and a rise through the luteal phase.
- Braxton Hicks Contractions Sporadic tightenings and relaxations of the uterine muscle that occur throughout pregnancy without causing cervical dilation, most often noticed in the second or third trimester.
- Brittle Nails Nails that split, peel, or break more easily than usual, documented in most hypothyroidism cases and linked to a spoon-shaped nail change in iron-deficiency anemia.
- Cold Hands & Feet Fingers and toes that feel cold more often or more intensely than the rest of the body, studied alongside thyroid function and distinct from Raynaud's phenomenon.
- Dry Skin Skin that feels rough, tight, flaky, or itchy from reduced moisture and oil, a documented symptom of hypothyroidism and the menopause transition.
- Finger Color Change The white-blue-red color sequence in fingers on cold or stress exposure, the primary logged sign of Raynaud's; tracked within the Raynaud's entry.
- Food Aversions A strong dislike or repulsion toward a specific food or smell that wasn't there before pregnancy, often beginning the same week as nausea in the first trimester.
- Heartburn in Pregnancy A burning sensation in the chest from stomach acid moving into the esophagus, driven mainly by progesterone relaxing the lower esophageal sphincter as pregnancy progresses.
- Heat Intolerance An unusual, ongoing sensitivity to heat or warm environments, documented as a common symptom of hyperthyroidism and distinct from the episodic waves of a hot flash.
- Migraine Aura A fully reversible set of neurological symptoms, most often visual, that develops gradually before or alongside a migraine headache, tied to cortical spreading depression.
- Morning Sickness (Nausea in Pregnancy) Nausea and, often, vomiting that begins early in pregnancy and usually peaks between weeks 10 and 16, linked to rising levels of the placental hormone GDF15.
- Muscle Weakness A reduction in the force a muscle can generate, distinct from fatigue, studied in connection with thyroid function and vitamin D status.
- Neck Swelling (Goiter) A visible or felt increase in the size of the thyroid gland at the base of the neck, studied alongside iodine intake and autoimmune thyroid disease.
- Painful Intercourse (Dyspareunia) Persistent or recurrent genital pain before, during, or after sex, studied in connection with causes including endometriosis and menopause.
- Pale Skin (Pallor) A lighter-than-usual skin tone caused by reduced blood flow or a lower red blood cell count, documented as a physical finding in iron-deficiency anemia.
- Pica & Ice Craving A persistent urge to eat or chew items with no nutritional value; pagophagia, an urge specifically for ice, is its most studied form and is linked to iron-deficiency anemia.
- Rewarming Pain Throbbing or stinging as blood flow returns to fingers or toes after a Raynaud's episode; tracked within the Raynaud's entry.
- Round Ligament Pain A sharp or pulling ache in the lower abdomen or groin from stretching of the uterine round ligament, most commonly reported in the second trimester.
- Seizure Logging (Catamenial Epilepsy) Logging seizures against cycle data reflects catamenial epilepsy, the well-studied pattern where seizure frequency rises and falls with the phases of the menstrual cycle.
- Tingling & Numbness (Paresthesia) A tingling, prickling, or numb sensation on the skin with no outside cause, reflecting sensory nerve signals firing abnormally on their way to the brain.
- Tremors An involuntary, rhythmic, oscillating movement of a body part, made more visible by triggers including hyperthyroidism and caffeine.
Conditions & Life Stages
- Adenomyosis A condition in which tissue resembling the uterine lining grows into the muscular wall of the uterus.
- Endometriosis A chronic condition in which tissue similar to the uterine lining grows outside the uterus, most often on the ovaries, fallopian tubes, and pelvic lining.
- Gestational Diabetes Glucose intolerance first recognized during pregnancy, driven by rising insulin resistance as pregnancy progresses.
- Hashimoto's Thyroiditis A chronic autoimmune condition in which the immune system gradually attacks the thyroid gland, the most common cause of hypothyroidism in iodine-sufficient countries.
- Hyperthyroidism A condition in which the thyroid gland produces more thyroid hormone than the body needs, speeding up metabolism.
- Hypothalamic Amenorrhea The absence of periods that occurs when brain-to-ovary signaling is suppressed, often linked to low energy availability or high training load.
- Hypothyroidism A condition in which the thyroid gland doesn't produce enough thyroid hormone to meet the body's needs.
- Insulin Resistance A state in which cells respond less to insulin's signal to take up glucose, so the body needs more insulin to hold blood sugar steady.
- Iron-Deficiency Anemia Anemia that develops when iron stores run too low to keep up with hemoglobin production, the most common cause of anemia worldwide.
- Perimenopause The menopausal transition, when ovarian hormone production becomes irregular in the years before menopause.
- Polycystic Ovary Syndrome (PCOS) A common hormonal condition involving some combination of irregular ovulation, elevated androgens, and polycystic ovarian morphology.
- Premenstrual Dysphoric Disorder (PMDD) A depressive disorder marked by severe mood and physical symptoms that appear before a period and ease within days of it starting.
- Premenstrual Syndrome (PMS) A group of physical and psychological symptoms that follow the menstrual cycle, showing up in the luteal phase and easing once bleeding begins.
- Primary Ovarian Insufficiency (POI) The loss of normal ovarian function before age 40, marked by irregular or absent periods with elevated FSH and low estradiol.
- Uterine Fibroids Common benign growths of smooth muscle and fibrous tissue that develop in or on the wall of the uterus.
- Celiac Disease A chronic autoimmune condition in which eating gluten damages the lining of the small intestine, linked to malabsorption of nutrients including iron, folate, and vitamin B12.
- Egg Freezing (Oocyte Cryopreservation) A fertility preservation procedure in which eggs are retrieved from the ovaries after hormonal stimulation and preserved by vitrification for potential future use.
- IBD (Crohn's Disease & Ulcerative Colitis) An umbrella term for Crohn's disease and ulcerative colitis, chronic conditions causing long-term digestive-tract inflammation that comes in flares.
- Raynaud's Syndrome An episodic narrowing of small blood vessels in the fingers and toes, usually triggered by cold or emotional stress, substantially more common in women.
How We Source This
Every physiological claim in this encyclopedia is cited to a real, verifiable source: peer-reviewed research where possible, or established references like NIH, StatPearls, or physiology textbooks for basic mechanism claims. If a claim can't be traced to a real source, we cut it rather than soften the citation.
Entries describe what a metric is, how it's measured, and what population-level research shows. They do not state clinical or lab reference ranges, do not interpret what a specific value means for an individual reader, and do not suggest testing or monitoring action. For anything about your own results, talk to your doctor.
Every reference is checked to confirm it resolves to a real title, authors, and journal, and that it actually supports the sentence it's attached to. Entries carry a review date, and we revisit them as the underlying research changes.
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