Evidence-Based Supplement & Herb Guides

Thyroxine-Binding Globulin (TBG) Test: High, Low, Normal Range, and Thyroid Hormones

Understand what a TBG blood test measures, why high or low levels alter total T4 and T3, common causes, normal ranges, and the right follow-up tests.

A thyroxine-binding globulin test measures the blood protein that carries most circulating T4 and T3. It is mainly used when total thyroid hormone results...

Total T3 (Triiodothyronine) Test: High, Low, Normal Range, and Hyperthyroidism Results

Learn how a total T3 blood test detects T3-predominant hyperthyroidism, what high or low results mean, typical ranges, interferences, and follow-up steps.

A total T3 test measures all triiodothyronine in the blood, including hormone attached to carrier proteins and the very small free portion. It is...

Total T4 (Thyroxine) Test: High, Low, Normal Range, and Thyroid Function

Understand total T4 testing, including normal ranges, high and low causes, binding-protein effects, pregnancy and newborn use, assay limits, and follow-up.

A total T4 test measures all thyroxine in the blood, including hormone bound to transport proteins and the small free fraction. T4 is the...

TSH Receptor Antibody (TRAb) Test: Graves Disease, Hyperthyroidism, and Results

Learn how TRAb testing confirms Graves disease, how positive or negative results are interpreted, how assays differ, and why TRAb matters in relapse and pregnancy.

A TSH receptor antibody test detects autoantibodies that attach to the thyroid’s TSH receptor. It is most often used to confirm Graves disease, the...

TSH With Reflex to Free T4 Test: Thyroid Screening, Abnormal Results, and Meaning

Understand how TSH with reflex to free T4 works, what abnormal result combinations mean, when the algorithm can miss disease, and which follow-up tests help.

A TSH with reflex to free T4 test is a laboratory algorithm rather than a single combined measurement. The laboratory measures thyroid-stimulating hormone first....

17-Hydroxyprogesterone (17-OHP) Test: Congenital Adrenal Hyperplasia, PCOS, and Results

Understand the 17-OHP test, common ranges, CAH and PCOS causes of high results, ACTH stimulation, timing, and the next steps after an abnormal value.

The 17-hydroxyprogesterone (17-OHP) test measures a steroid made mainly in the adrenal glands and, to a smaller extent, the ovaries and testes. Its main...

Androstenedione Blood Test: High, Low, PCOS, Adrenal, and Fertility Results

Learn what an androstenedione blood test shows, why levels may be high or low, how PCOS and adrenal causes differ, and which follow-up tests help.

An androstenedione blood test measures a weak androgen made by the adrenal glands and gonads. The body can convert it into testosterone or estrogens,...

Anti-Mullerian Hormone (AMH) Test: Ovarian Reserve, Fertility, and Results

Understand AMH testing for ovarian reserve, fertility treatment response, high and low results, PCOS, age effects, limitations, and useful next steps.

The anti-Müllerian hormone (AMH) test estimates the pool of small growing ovarian follicles and is widely used to predict how the ovaries may respond...

Bioavailable Testosterone Test: High, Low, Normal Range, and Results

Understand bioavailable testosterone, how SHBG and albumin affect results, causes of high or low levels, testing methods, and safe follow-up steps.

A bioavailable testosterone test estimates the testosterone that is not tightly bound to sex hormone-binding globulin (SHBG). It includes free testosterone plus testosterone loosely...

Day 21 Progesterone Test: Ovulation Confirmation, Luteal Phase, Normal Range, and Results

Learn when to schedule a day 21 progesterone test, what levels can confirm ovulation, why low results occur, and why one value cannot grade luteal quality.

A “day 21” progesterone test checks whether ovulation likely occurred by measuring progesterone during the luteal phase. The name assumes a 28-day cycle with...

Dehydroepiandrosterone Sulfate (DHEA-S) Test: High, Low, Normal Range, and Results

Understand the DHEA-S test, age-specific ranges, adrenal causes of high or low results, links with PCOS and CAH, and the follow-up tests that help.

A dehydroepiandrosterone sulfate (DHEA-S) test measures the most abundant circulating adrenal androgen. Because the adrenal glands produce nearly all DHEA-S, the result helps identify...

Delayed Puberty Hormone Test Panel: LH, FSH, Estradiol, Testosterone, and Results

Understand delayed puberty hormone testing with LH, FSH, estradiol, and testosterone, common result patterns, age cutoffs, causes, and next steps.

A delayed puberty hormone panel measures signals from the pituitary gland and sex hormones from the ovaries or testes to help explain why puberty...

Estradiol (E2) Test: High, Low, Normal Range, Fertility, and Menopause Results

Understand estradiol testing, cycle and menopause ranges, causes of high or low E2, fertility uses, related hormone patterns, and next steps after results.

An estradiol (E2) test measures the most active estrogen during the reproductive years. It helps evaluate menstrual changes, fertility treatment, ovarian function, puberty, menopause-related...

Estriol (E3) Test: Pregnancy, Placenta Health, and Results

Understand estriol testing in pregnancy, how uE3 and MoM support prenatal screening, causes of low results, and follow-up options after an abnormal screen.

An estriol (E3) test measures an estrogen produced in large amounts during pregnancy through cooperation between the fetus and placenta. Maternal serum unconjugated estriol...

Estrogen Levels Test: Estradiol, Estrone, Estriol, High and Low Results, and Meaning

Learn how estradiol, estrone, and estriol tests differ, what high or low estrogen results may mean, how life stage affects ranges, and which follow-up helps.

An estrogen levels test may measure estradiol (E2), estrone (E1), estriol (E3), or more than one form, depending on the clinical question. Estradiol is...

Estrone (E1) Test: Menopause, Estrogen Levels, High and Low Results

Understand estrone testing in menopause and other settings, why E1 may be high or low, how it differs from estradiol, and what follow-up is useful.

An estrone (E1) test measures an estrogen produced in the ovaries, adrenal-related pathways, and especially through conversion of androgens in fat and other tissues....

Fertility Hormone Test Panel: FSH, LH, Estradiol, AMH, Progesterone, Prolactin, and Results

Understand fertility hormone panels, the timing and meaning of FSH, LH, estradiol, AMH, progesterone, and prolactin, and the limits of normal results.

A fertility hormone test panel combines measurements that answer different questions about ovarian reserve, ovulation, pituitary signaling, and menstrual function. FSH and estradiol are...

Follicle-Stimulating Hormone (FSH) Test: High, Low, Normal Range, Fertility, Menopause, and Results

Understand FSH testing, normal cycle and menopause patterns, causes of high or low results, fertility limits, and how related hormones guide next steps.

A follicle-stimulating hormone (FSH) test measures a pituitary signal that supports ovarian follicle development and sperm production. In women, FSH changes across the menstrual...

Free Testosterone Test: High, Low, Normal Range, SHBG, and Hormone Balance

Understand free testosterone testing, how SHBG changes results, reliable measurement methods, causes of high or low levels, and safe follow-up steps.

A free testosterone test measures or estimates the small fraction of testosterone not bound to proteins. It is most useful when total testosterone and...

Gonadotropin-Releasing Hormone (GnRH) Stimulation Test: Puberty, Pituitary, and Results

Understand the GnRH stimulation test for early or delayed puberty, how LH and FSH responses are interpreted, protocol limits, and the next steps after results.

A gonadotropin-releasing hormone (GnRH) stimulation test evaluates how the pituitary releases luteinizing hormone (LH) and follicle-stimulating hormone (FSH) after a GnRH-type medicine. It is...