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Cortisol, sex hormones and the mineral panel

17 min

Skills you'll build4 skills
  • Confirm draw time, posture, and chilling for cortisol, renin, and ACTH specimens
  • Read a cortisol result against the limits of its timed draw or dynamic test
  • Read FSH, LH, estradiol, and progesterone against the interval for cycle day and age
  • Judge whether a PTH fits the calcium, phosphate, vitamin D, and kidney results

At the bench: Check specimen identity and suitability before analysis · Review electrolyte results and related calculations for consistency

Try first

Try first

A cortisol drawn at 16:00 on a medical ward reads 6.0 µg/dL. The request asks whether the patient has adrenal insufficiency. What does this result show?

Keep going to see the reasoning.

Keep going to see the reasoning.

Keep going to see the reasoning.

Right. Keep going to follow the reasoning.

Keep going to see the reasoning.

Get the idea

Use the explanation to check your first decision.

Collection requirements for hormone tests

Hormone decision limits assume a defined collection time and handling. A result from a specimen collected outside those conditions cannot be compared with the limit.1

TestDrawHandling
Cortisol8 to 9 AM for the published limits, with the time recordedNo temperature requirement
ACTH7 to 10 AM, before any glucocorticoid dosePrechilled EDTA, onto ice at once, cold centrifuge, plastic aliquot, frozen
ReninMid-morning, after 2 hours upright, then seated 5 to 15 minutesEDTA at room temperature, separated promptly
FSH, LH, estradiolCycle days 2 to 5, with the cycle day on the requestSerum
ProgesteroneMid-luteal, about 7 days before expected mensesSerum

ACTH and renin need opposite temperatures. ACTH left at room temperature is degraded and reads falsely low. Whole blood chilled before separation undergoes cryoactivation, and renin reads falsely high.1,2

Interpreting cortisol

Cortisol is released in pulses with a morning peak. A random cortisol neither confirms nor excludes adrenal insufficiency.1

  • For suspected central insufficiency, an 8 to 9 AM cortisol below 3 µg/dL is indicative. A value above 15 µg/dL makes it unlikely, and values in between need stimulation testing.3
  • For suspected primary insufficiency, a morning cortisol below 5 µg/dL with an ACTH above twice the upper reference limit localizes the defect to the adrenal gland.4
  • Binding globulin carries most cortisol. Estrogen raises the total. Hypoalbuminemia and critical illness lower it with little change in free cortisol.5

Regulating hormones and their targets

Gonadal axis. High LH and FSH with a low sex steroid mean the gonad has failed. Low or inappropriately normal gonadotropins with a low steroid point to the pituitary or hypothalamus. Each result is read against the interval for the cycle day, age and reproductive stage.1

Mineral axis. Rising ionized calcium suppresses PTH secretion. A PTH inside its interval beside hypercalcemia is therefore inappropriately normal, and it fits primary hyperparathyroidism.6 Low vitamin D and reduced kidney function raise PTH appropriately, so 25-hydroxyvitamin D and creatinine are read with it.6,7

Follow the bench demonstration

Sources for this step
References
  1. Rifai N, Chiu RWK, Young I, Burnham CAD, Wittwer CT, eds. Tietz Textbook of Laboratory Medicine. 7th ed. Elsevier; 2023.
  2. Adler GK, Stowasser M, Correa RR, et al. Primary aldosteronism: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2025;110(9):2453-2495. doi:10.1210/clinem/dgaf284
  3. Fleseriu M, Hashim IA, Karavitaki N, et al. Hormonal replacement in hypopituitarism in adults: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2016;101(11):3888-3921. doi:10.1210/jc.2016-2118
  4. Bornstein SR, Allolio B, Arlt W, et al. Diagnosis and treatment of primary adrenal insufficiency: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2016;101(2):364-389. doi:10.1210/jc.2015-1710
  5. Choi MH. Clinical and technical aspects in free cortisol measurement. Endocrinol Metab (Seoul). 2022;37(4):599-607. doi:10.3803/EnM.2022.1549
  6. Bilezikian JP, Khan AA, Silverberg SJ, et al. Evaluation and management of primary hyperparathyroidism: summary statement and guidelines from the Fifth International Workshop. J Bone Miner Res. 2022;37(11):2293-2314. doi:10.1002/jbmr.4677
  7. Makris K, Bhattoa HP, Cavalier E, et al. Recommendations on the measurement and the clinical use of vitamin D metabolites and vitamin D binding protein: a position paper from the IFCC Committee on Bone Metabolism. Clin Chim Acta. 2021;517:171-197. doi:10.1016/j.cca.2021.03.002

Watch one

Read each decision and its explanation.

An adult woman's outpatient mineral panel comes to you for review.

Does the PTH fit the rest of the panel?

TestResultReference intervalFlag
Calcium, ionized1.45 mmol/L High1.15–1.33 mmol/L1.15–1.33High
Calcium, total11.2 mg/dL High8.6–10.3 mg/dL8.6–10.3High
Albumin4.2 g/dL3.5–5.0 g/dL3.5–5.0
Phosphate2.3 mg/dL Low2.5–4.5 mg/dL2.5–4.5Low
PTH, intact58 pg/mL15–65 pg/mL15–65
25-hydroxyvitamin D31 ng/mL20–50 ng/mL20–50
Creatinine0.82 mg/dL0.59–1.04 mg/dL0.59–1.04

Specimen: H 10, L 20, I 1. Serum and heparinized whole blood for ionized calcium, drawn together

  1. Confirm the calcium. Ionized calcium is high at 1.45 mmol/L, and the total calcium agrees, with albumin within its interval.

    The parathyroid glands sense ionized calcium, so interpretation starts with it.

  2. Compare PTH with the calcium. A PTH of 58 pg/mL is within its interval, which is inappropriately normal for this calcium.

    Normal parathyroid glands respond to high calcium by suppressing PTH to low or undetectable levels.

  3. Check the phosphate. At 2.3 mg/dL it is low, which fits ongoing PTH action.

    PTH increases renal phosphate excretion.

  4. Check vitamin D and kidney function. A 25-hydroxyvitamin D of 31 ng/mL and a creatinine of 0.82 mg/dL show that neither is driving the PTH.

    Vitamin D deficiency and reduced filtration raise PTH appropriately and would change the interpretation.

The PTH of 58 pg/mL does not fit a high ionized calcium of 1.45 mmol/L. With the low phosphate, the pattern fits primary hyperparathyroidism.

Practice this skill

Your turn

Problem 1 of 3 · Hints available

LH and FSH are elevated and estradiol is low in a specimen from a 58-year-old woman whose menses stopped 6 years ago. How should the laboratory read this pattern?

Correct. After menopause the ovary no longer supplies estradiol and inhibin, so negative feedback on the pituitary is lost. High gonadotropins with low estradiol fit her age and reproductive stage.

Incorrect. Central hypogonadism has low or inappropriately normal gonadotropins, and these are elevated.

Incorrect. The premature ovarian insufficiency criteria apply to women younger than 40. At 58, with menses stopped for 6 years, the same hormones fit expected menopause.

Hint
  1. Start with the gonadotropins and ask which way they moved.
  2. Check which interval fits her age and reproductive stage.

Review Gonadal laboratory patterns

Problem 2 of 3 · Hints available

Why can a low total cortisol be difficult to interpret in a specimen from someone with markedly reduced cortisol-binding proteins?

Incorrect. With less binding protein, less cortisol is carried bound, so the total falls even when adrenal output is unchanged. Check binding status before reading a low total as insufficiency.

Incorrect. The effect is physiologic. With less binding protein, less cortisol is protein-bound, so the total falls with little change in the unbound fraction.

Correct. Corticosteroid-binding globulin and albumin carry most serum cortisol, so their loss lowers the total without an equal fall in free cortisol. A measure of the unbound fraction, serum free cortisol or salivary cortisol, is preferred in these states.

Hint
  1. Most serum cortisol circulates bound to proteins.
  2. Ask which fraction a total cortisol measures, and which fraction acts on tissues.

Review Cortisol and ACTH

Problem 3 of 3 · On your own

An adult man's panel shows total calcium 8.1 mg/dL with albumin 4.0 g/dL, phosphate 2.4 mg/dL, intact PTH 142 pg/mL (reference interval 15 to 65 pg/mL), 25-hydroxyvitamin D 9 ng/mL and creatinine 0.9 mg/dL. Alkaline phosphatase is above its interval. Which pattern fits?

Primary hyperparathyroidism raises calcium. Here the calcium is low, and the high PTH is the parathyroid response to it.

Hypoparathyroidism has a low or undetectable PTH with a high phosphate. This PTH is more than twice its upper limit.

Kidney disease retains phosphate and raises creatinine. Here the phosphate is low and the creatinine is within its interval.

A 25-hydroxyvitamin D of 9 ng/mL limits calcium absorption, and the parathyroid glands raise PTH in response to the low calcium. The high alkaline phosphatase fits the defective mineralization of vitamin D deficiency.

Review Reading the mineral panel together

Use it

Read the case evidence, then make each decision. The step is complete without it.

  • An outpatient woman is tested for suspected primary adrenal insufficiency.
  • The requisition records an 08:40 draw after 2 hours upright and 10 minutes seated, and no glucocorticoid taken.
  • ACTH went into a prechilled EDTA tube and onto ice at once.
  • The collector put the renin EDTA tube and the cortisol tube in the same ice bag for the 40-minute transport.
  • Your procedure requires renin whole blood to stay at room temperature until it is separated.
TestResultReference intervalFlag
Cortisol3.8 µg/dL Low5.0–25.0 µg/dL5.0–25.0Low
ACTH180 pg/mL High7.2–63.3 pg/mL7.2–63.3High
Renin activity6.1 ng/mL/h High0.6–4.3 ng/mL/h0.6–4.3High

Specimen: H 6, L 12, I 1. Drawn 08:40, renin EDTA tube transported on ice with the ACTH tube

Decision 1 of 3

What do you do with the renin?

Chilled whole blood undergoes cryoactivation, so this renin is falsely high regardless of the patient's true value. A renin from this tube cannot be interpreted.

Applied a hormone decision limit to an unsuitable collection

Cortisol decision limits assume an 8 to 9 AM draw, renin needs upright posture and room-temperature handling, and ACTH needs prechilled EDTA on ice. Comparing a result collected outside those conditions with the published limit can report a normal level as abnormal or an abnormal one as normal.

A comment leaves a falsely high result in the record, where it would still be compared with the interval.

Chilling before separation raises renin in the tube, and the laboratory cannot reverse it. A new specimen handled at room temperature gives a renin that can be interpreted.

The cryoactivation happened in the tube. A repeat measures the same raised renin.

Review Timing, posture, tube, and temperature

Decision 2 of 3

What do you do with the ACTH and the cortisol?

ACTH was drawn before any glucocorticoid into prechilled EDTA and kept on ice, which is its required handling. Cortisol has no temperature requirement, and both were drawn in the morning window.

ACTH requires ice, and ice does not affect cortisol. Only renin is affected by chilling.

The ACTH met every handling rule: prechilled EDTA, ice at once, and a morning draw before any glucocorticoid.

Review Timing, posture, tube, and temperature

Decision 3 of 3

How do the cortisol and ACTH read together?

A morning cortisol below 5 µg/dL beside an ACTH above twice its upper limit shows the pituitary stimulating an adrenal gland that does not respond. The defect is in the adrenal gland.

Central insufficiency comes with a low or inappropriately normal ACTH. An ACTH of 180 pg/mL shows the pituitary responding.

Read the target hormone without its regulating hormone

A low free T₄ beside a high TSH places the failure in the thyroid gland. A low free T₄ beside a low or inappropriately normal TSH places it in the pituitary or hypothalamus. Reading the target hormone alone cannot localize the defect.

This cortisol was drawn at 08:40 and is paired with its ACTH, so it meets the conditions of the morning limits.

Judged adrenal function from a random cortisol

Cortisol is episodic with a morning peak, and the published limits assume a timed draw or a stimulation or suppression protocol. A random cortisol neither confirms nor excludes insufficiency. Reading it against those limits can report adrenal failure, or a normal axis, that the protocol would not show.

Review Cortisol and ACTH

Each tube's handling was checked against its own requirement:

  • ACTH requires ice, and it was transported on ice.
  • Cortisol has no temperature requirement.
  • Renin must stay at room temperature, and it was transported on ice.

The ACTH and cortisol are released, and the renin is redrawn and kept at room temperature.

For reference

Sources checked