Understanding Hormone Blood Tests: Cortisol, DHEA-S, Testosterone, and More

Why Hormone Tests Require Extra Context

Hormones are among the most context-dependent biomarkers in medicine. Most fluctuate across the day, respond acutely to stress, sleep, and food, and have wide reference ranges that overlap considerably between healthy and symptomatic individuals. Understanding what each hormone measures—and the conditions that affect it—is essential for making sense of your results.

Cortisol: The Stress Hormone With a Strict Schedule

Cortisol is produced by the adrenal glands and follows a strong diurnal rhythm: levels peak within 30–60 minutes of waking (the cortisol awakening response) and fall steadily through the day to their nadir around midnight.[2] A morning cortisol drawn between 8–9 a.m. is the standard clinical measurement, with typical reference ranges of 6–23 µg/dL. Afternoon samples yield much lower values and are not directly comparable.

Chronically elevated cortisol—as seen in Cushing's syndrome—leads to weight gain, hypertension, glucose intolerance, and skin changes.[3] Chronically low cortisol suggests adrenal insufficiency, which can cause fatigue, low blood pressure, and electrolyte abnormalities. Acute stress, illness, or even the anxiety of a blood draw can transiently elevate cortisol,[2] which is why borderline results are typically confirmed with additional testing such as a 24-hour urine free cortisol or low-dose dexamethasone suppression test.[3]

DHEA-S: The Adrenal Reserve Marker

DHEA-S (dehydroepiandrosterone sulfate) is the sulfated storage form of DHEA, secreted almost exclusively by the adrenal glands. Unlike cortisol, DHEA-S has a relatively stable level throughout the day, making it a more practical marker of adrenal androgen output. It peaks in young adulthood and declines steadily with age—a process sometimes called adrenopause.

Very low DHEA-S can accompany adrenal insufficiency or extreme physiologic stress such as critical illness. Elevated DHEA-S in women may indicate polycystic ovary syndrome (PCOS) or an adrenal tumor.[5] DHEA-S is often tested alongside cortisol to distinguish adrenal causes of androgen excess from ovarian causes, since the ovaries do not produce DHEA-S in significant quantities.

Testosterone: Free vs. Total and Why It Matters

Testosterone circulates in two main forms: bound to proteins (primarily sex hormone-binding globulin, or SHBG, and albumin) and unbound. Total testosterone measures both fractions, while free testosterone measures only the biologically active unbound portion. In most cases, low symptoms with a normal total testosterone prompt a free testosterone measurement, because elevated SHBG—common with aging, hyperthyroidism, or liver disease—can reduce free testosterone while keeping the total within range.[1]

Normal total testosterone ranges are approximately 300–1,000 ng/dL in men and 15–70 ng/dL in women. In men, symptoms of deficiency (low libido, fatigue, loss of muscle mass, mood changes) typically align with levels below 300 ng/dL, though some men are symptomatic at higher levels depending on their free testosterone.[1] In women, testosterone plays a role in libido, energy, and bone density; both deficiency and excess (as seen in PCOS or adrenal disorders) carry clinical significance.[5]

Testosterone should be drawn in the morning when levels are at their daily peak for men—typically between 7–10 a.m. A single low value is usually confirmed with a repeat test on a different day before initiating any treatment.[1]

FSH: The Pituitary Signal That Reveals Gonadal Function

FSH (follicle-stimulating hormone) is secreted by the pituitary gland to stimulate the gonads. In women, FSH drives follicle development in the ovaries and is the primary marker for assessing ovarian reserve. A high FSH on day 2–3 of the menstrual cycle—particularly above 10–12 IU/L—suggests diminished ovarian reserve or impending menopause.[4] In women over 45 with amenorrhea, an FSH consistently above 40 IU/L is consistent with menopause.

In men, FSH stimulates sperm production. Elevated FSH in men indicates primary testicular failure (the pituitary is signaling harder because the testes are not responding adequately), while low FSH alongside low testosterone points toward secondary hypogonadism originating in the pituitary or hypothalamus. This distinction is clinically important because it guides the direction of further investigation and treatment.

Reading Your Hormone Panel as a System

Just as thyroid hormones must be interpreted as an axis, adrenal and sex hormones form interrelated systems. Cortisol and DHEA-S reflect adrenal health together; testosterone and FSH reveal whether a hormonal problem originates in the gland or in the pituitary signal. Tracking values over time—using a tool like Health3—helps you see whether a low result is a stable baseline or part of a declining trend that warrants attention.

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