Your activity: 6 p.v.

Measurement of cortisol in serum and saliva

Measurement of cortisol in serum and saliva
Author:
Lynnette K Nieman, MD
Section Editor:
André Lacroix, MD
Deputy Editor:
Kathryn A Martin, MD
Literature review current through: Dec 2022. | This topic last updated: Sep 29, 2019.

INTRODUCTION — Measurements of cortisol in serum (or occasionally plasma) are extremely useful in the diagnosis of hypercortisolism and adrenal insufficiency. It is important to appreciate the many factors that can affect the serum cortisol concentration and in particular the episodic secretion of cortisol and the resulting diurnal variation in serum cortisol, which makes the interpretation of a single value hazardous. Measurements of the salivary cortisol may offer some advantages over measurements of serum cortisol. Methods of interpretation of cortisol assays will be reviewed here. Their use in the diagnosis of adrenal disorders is reviewed separately. (See "Establishing the diagnosis of Cushing's syndrome" and "Diagnosis of adrenal insufficiency in adults".)

MEASUREMENT OF SERUM CORTISOL — Cortisol has been measured in serum by several methods [1]. Although many of them are no longer in routine use, the important assays are mentioned to permit one to interpret the older literature.

Methods of measurement

Porter-Silber chromogens — Serum cortisol was first measured by assay of Porter-Silber chromogens (17,21-dihydroxy-20-ketosteroids, referred to as 17-hydroxycorticosteroids, or 17-OHCS) [2]. This method is no longer used.

Competitive protein-binding assay — This assay uses competition for binding sites on cortisol-binding globulin (CBG, or transcortin) to quantify cortisol [3,4]. Its advantage is lack of drug interference; its disadvantage is that prednisolone and several endogenous steroids, some of which may be increased in pregnancy, adrenal carcinoma, congenital adrenal hyperplasia, and after administration of adrenal enzyme inhibitors, bind to CBG and falsely elevate serum cortisol values. Interfering steroids can be removed before assay by solvent partition or thin layer chromatography (TLC).

Fluorometric assay — This assay exploits the fluorescence of 4-11-beta, 21-dihydroxy-3,20-ketosteroids (11-hydroxycorticosteroids, or 11-OHCS) in sulfuric acid and alcohol [5]. Cortisol and corticosterone are detected by this assay; potent synthetic glucocorticoids are not. Its advantages are simplicity and relative specificity; its disadvantage is that spironolactone, quinine, quinidine, niacin, and benzoyl alcohol also fluoresce in those solvents and therefore falsely elevate cortisol values.

Radioreceptor assay — This assay uses the type II glucocorticoid cytosol receptor as a cortisol-binding agent [6]. Its advantage is its specificity for bioactive steroids, including synthetic glucocorticoids; its disadvantage is the limited supply and instability of the receptor. As a result, this assay is not widely available.

Radioimmunoassay — Radioimmunoassays for cortisol use polyclonal or monoclonal antibodies that are raised to a cortisol analogue that has been conjugated to a protein carrier. Each antibody is characterized in terms of its affinity and crossreactivity with other endogenous or exogenous steroids found in serum. Antibody, labeled cortisol tracer, and cortisol standard are used to perform the assay. The results are dependent upon the specificity of the antibody used in the assay. Both liquid-phase and solid-phase assays of requisite sensitivity and specificity are widely available in reference laboratories and in kit form. Serum total cortisol is measured.

Other immunoassays — Variations on radioimmunoassays using fluorescent, chemiluminescent, and other labels in place of radioisotopic labels, and two-site antibody designs (one antibody is bound to a solid substrate, the other carries the radioactive or other label, and the steroid forms a bridge between them) have similar sensitivity and specificity and are available for use in automated analyzers. The results, like those of radioimmunoassay, are dependent upon the specificity of the antibody used in the assay [7].

Structurally-based assays — In contrast to antibody-based assays, structurally-based assays (HPLC, mass spectrometry) are highly specific for the cortisol molecule; they also can measure synthetic steroids [8]. The development of high-throughput techniques to simultaneously measure multiple samples makes these labor-intense assays feasible for commercial use [9]. This method separates cortisol from other steroids and steroid metabolites; cortisol is then measured fluorometrically or spectrophotometrically [10].

Normal values — The serum cortisol concentration normally reflects that of corticotropin (ACTH) and therefore has circadian rhythmicity (figure 1). Normal values vary with the particular assay. The following values are representative of an average radioimmunoassay; those obtained by competitive protein binding assay would be similar, and fluorometric assay results are about 3 mcg/dL (85 nmol/L) higher [11].

In normal subjects serum cortisol concentrations are higher in the early morning (about 6 AM), ranging from 10 to 20 mcg/dL (275 to 555 nmol/L). Serum cortisol concentrations range from 3 to 10 mcg/dL (85 to 275 nmol/L) at 4 PM, and the concentrations are lowest, less than 5 mcg/dL (140 nmol/L), one hour after the usual time of sleep.

Interpretation — Cortisol secretion is episodic and the normal ranges are broad. A single serum value, if it falls within the normal range, is inconclusive. An individual can have partial pituitary or adrenal insufficiency but maintain plasma ACTH and serum cortisol concentrations within their respective normal ranges. For these reasons, stimulation or suppression testing should be performed when there is doubt. Nevertheless, samples drawn at the appropriate time for the suspected endocrine dysfunction can be very helpful in excluding adrenal hypofunction or hyperfunction.

Patients with primary or secondary adrenal insufficiency have low early morning serum cortisol concentrations. If the value is greater than 10 mcg/dL (276 nmol/L), it is unlikely that the patient has clinically important adrenal insufficiency, whereas if it is less than 3 mcg/dL (83 nmol/L), the probability of adrenal insufficiency is high. (See "Diagnosis of adrenal insufficiency in adults".) Since serum cortisol is often undetectable one hour after the beginning of sleep, measurement at this time does not identify patients with adrenal insufficiency.

Patients with congenital adrenal hyperplasia may have normal or low serum cortisol values (corresponding to simple virilizing and "late-onset" CYP21A2 deficiency types) in the early morning.

Most patients with Cushing's syndrome have early morning serum cortisol concentrations within or slightly above the normal range. In contrast, serum cortisol concentrations one hour after sleep are almost always high (greater than 7.5 mcg/dL [207 nmol]) and are often equal to the early morning values (ie, they have an abnormal or absent circadian rhythm) [12]. (See "Establishing the diagnosis of Cushing's syndrome".)

Important caveats — Cortisol secretion normally reflects ACTH secretion. As a result, the same caveats concerning circadian rhythmicity, stress, and glucocorticoid administration also pertain to it, except that recent hydrocortisone (cortisol) or cortisone administration may result in high serum cortisol concentrations. The longer disappearance half-time of cortisol than of ACTH (about 80 versus eight minutes) and the several minute lag in its secretion after ACTH stimulation tend to damp excursions in serum cortisol relative to those of ACTH.

Several other factors must be considered in interpreting serum cortisol results.

CBG — Serum cortisol concentrations do not correlate well with cortisol production rates unless the CBG concentration is accounted for [13]. Hepatic CBG synthesis is increased by estrogens [14-16], and early morning serum total cortisol concentrations of 50 mcg/dL (1400 nmol/L) or higher are not unusual during pregnancy or high dose oral contraceptive use [17,18]. Cortisol dissociates rapidly from CBG, so that early morning values are usually normal in these women. Insulin and insulin-like growth factor-1 inhibit CBG secretion in vitro, and serum CBG concentrations inversely correlated with indexes of insulin secretion such as fasting serum glucose concentrations and A1C are values [19]. Serum CBG concentration is increased in obese patients who have glucose intolerance. Some individuals have low levels of CBG on a genetic basis.

CBG levels are decreased in hyperinsulinemic states, hyperthyroidism, severe liver disease, and nephrotic syndrome. Some individuals have low levels of CBG on a genetic basis.

Hepatic and renal dysfunction — Even relatively severe hepatic dysfunction has little effect on serum cortisol concentrations [20]. Renal failure also has little effect on them, although retained cortisol metabolites may interfere in some radioimmunoassays [21].

Thyroid hormone — Thyroid hormone regulates the rate of cortisol metabolism, but hypothalamic-pituitary feedback mechanisms are intact and serum cortisol concentrations are within normal limits in patients with hypothyroidism or hyperthyroidism.

Body weight — Body weight has no appreciable effect on serum cortisol concentrations, but severe malnutrition apparently has a greater inhibitory effect on cortisol metabolism than on cortisol production, increasing serum cortisol concentrations slightly [22].

Age — It requires one year or more for infants to establish an adult sleep-wake cycle, entrain their circadian rhythms, and establish an adult pattern of ACTH and cortisol secretion [23]. Except for these changes in infants and the fact that, for the first several days of life, normal infants produce more cortisone than cortisol and have low serum cortisol concentrations [24], age has no effect on serum cortisol concentrations.

Depression — Major depressive disorders, especially severe melancholic depression, can result in cortisol dynamics similar to those of Cushing's disease [25-27]. However, most ambulatory patients with major depression have normal hour-of-sleep serum cortisol concentrations.

Synthetic glucocorticoids — Exogenously administered glucocorticoids can alter serum cortisol values either directly, if they cross-react with an antibody, leading to spurious elevations, or indirectly, if they suppress the hypothalamic-pituitary-adrenal axis, leading to low values. (See "Diagnosis of adrenal insufficiency in adults".)

Cross-reactivity depends upon the specificity of the antibody for cortisol. This possibility is evaluated during the development of antibody-based commercial assays and the results are available in the assay kit instructions, or from the company.

In contrast to antibody-based assays, structurally-based assays (HPLC, mass spectrometry) are highly specific for the cortisol molecule; they also can measure synthetic steroids [8]. The development of high-throughput techniques to simultaneously measure multiple samples makes these labor-intense assays feasible for commercial use [9]. Such assays are useful to evaluate surreptitious ingestion of synthetic steroids or potential cross-reaction in an antibody-based assay.

Depending upon the dose and duration of exogenous glucocorticoid administration, serum cortisol values may also be suppressed, reflecting secondary adrenal insufficiency. If this is the case, medications should be tapered rather than stopped for testing. (See "Glucocorticoid withdrawal".)

Non-glucocorticoid drugs — Several drugs induce hepatic cytochrome P-450 enzymes that metabolize steroids. Barbiturates, phenytoin, rifampin, aminoglutethimide, and mitotane increase the metabolic clearance of steroids and of metyrapone. They have a preferential effect on synthetic 9-fluoro steroids (eg, dexamethasone and fludrocortisone) as compared with natural steroids.

These drugs do not alter serum cortisol concentrations in normal subjects, but they can interfere with dexamethasone suppression and metyrapone stimulation tests and necessitate increased steroid replacement dose in patients with adrenal insufficiency.

Alcohol abuse — Alcohol abuse sufficient to increase serum hepatic enzyme concentrations, especially gamma-glutamyltransferase, can cause pseudo-Cushing's syndrome and high serum cortisol concentrations [28].

Sepsis — Patients with severe illness and sepsis have reduced CBG and albumin levels that result in lower serum cortisol levels [29,30].

SERUM FREE CORTISOL — The biologically active fraction of cortisol in serum is free cortisol. Although a variety of methods have been developed for measuring serum free cortisol [6,31-34], they are technically demanding and expensive and are not in general use. However, recent reports of decreased total cortisol levels in sepsis and critical illness have led to increased interest in measurement or calculation of free cortisol levels in these patients [29,30,35]. (See "Initial testing for adrenal insufficiency: Basal cortisol and the ACTH stimulation test", section on 'Critical illness'.)

CORTISOL PRECURSORS — Several biosynthetic precursors of cortisol, including pregnenolone, 17-hydroxypregnenolone, progesterone, 17-hydroxyprogesterone, and 11-deoxycortisol, can be measured by radioimmunoassay directly or after solvent partition and/or chromatography [32,36].

Normal values — The normal values for these compounds are as follows:

Serum 11-deoxycortisol is undetectable in normal subjects by current assays (ie, <1 mcg/dL or 30 nmol/L at 8 AM).

The early morning serum 17-hydroxyprogesterone concentration ranges from 60 to 300 ng/dL (1.8 to 19 nmol/L60 to 300 ng/dL) in men, 20 to 100 ng/dL (0.6 to 3 nmol/L) in women during the follicular phase of the menstrual cycle, 50 to 350 ng/dL (1.5 to 10.6 nmol/L) during the luteal phase, and 600 ng/dL (18 nmol/L) and more by the end of pregnancy.

Interpretation — These assays are not commonly used for assessment of hypothalamic-pituitary-adrenal function, but some of them do have specific applications.

Serum 17-hydroxyprogesterone can be measured before and after administration of cosyntropin (ACTH) in patients expected to have the 21-hydroxylase (P-450c21) deficiency variant of congenital adrenal hyperplasia [37,38]. Return of the early morning serum 17-hydroxypregnenolone or 17-hydroxyprogesterone concentration to normal can be used as an index of the adequacy of treatment in this disorder [39].

Serum 11-deoxycortisol can be measured in tests of pituitary ACTH secretory reserve using metyrapone [40]. (See "Metyrapone stimulation tests".)

One or more of these cortisol precursors may be increased in the serum of patients with adrenal carcinoma [41].

MEASUREMENT OF SALIVARY CORTISOL CONCENTRATION — Serum free cortisol diffuses freely into saliva. Therefore, measurements of salivary cortisol more accurately reflect serum free cortisol concentrations than do measurements of serum total cortisol [7]. The salivary cortisol concentration is independent of salivary flow rate [42,43].

Assay — Saliva (2.5 mL) is obtained after rinsing the mouth but before brushing the teeth, either by unstimulated flow or after chewing uncoated gum or a cotton tube (Plain Salivette, Sarstedt, Newton, NC), and can be stored at room temperature for many days [44] or frozen for extended periods. The sample is thawed, centrifuged at 1500 x g for 10 min at 4°C, and 2 mL of the supernatant is added to 10 mL of dichloromethane [45]. The dichloromethane is aspirated and evaporated, and the dried extract is reconstituted in assay buffer and assayed by competitive protein-binding assay [3,46], radioimmunoassay [46,47], or enzyme immunoassay [48]. Radioimmunoassay of unextracted saliva has also been described [49,50].

With the development of high-affinity antisera that react specifically with the D ring of cortisol, sensitivity has been improved, and interference by other steroids has been minimized.

Normal values — Salivary cortisol concentrations vary diurnally, with concentration of about 5.6 ng/mL (15.4 nmol/L) at 8 to 9 AM and about 1 ng/mL (2.8 nmol/L) at 11 PM [45,47,50] (table 1). The values in obese men and women are similar [45]. Additional work is needed to evaluate the late night normal range in older patients with medical illness [51].

Interpretation — Morning salivary cortisol concentrations are decreased in adrenal insufficiency, while late evening salivary cortisol concentrations are increased in Cushing's syndrome. Both the competitive protein-binding assay and cortisol radioimmunoassays crossreact with other steroids. The competitive protein-binding assay crossreacts with 17-hydroxyprogesterone and 11-deoxycortisol, for example; as a result, cortisol values may be artifactually increased in patients with congenital adrenal hyperplasia and adrenal carcinoma or after metyrapone administration. Some radioimmunoassays are more specific. Cortisol can be chromatographically separated from other steroids before assay in these situations [45].

More recently, developments of liquid chromatography mass spectrometry methods with less cross-reactivity than antibody-based methods, may yield fewer false positive results when used for the diagnosis of Cushing's syndrome [52].

Measuring salivary cortisol is especially useful in assessing cortisol secretion serially in ambulatory patients, who can collect multiple samples and store them in a refrigerator or freezer or even at room temperature for several days between clinic visits. They are also helpful in the evaluation of patients suspected of having cyclical Cushing's syndrome [47,53-56]. (See "Establishing the diagnosis of Cushing's syndrome".)

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Diagnosis and treatment of Cushing's syndrome".)

SUMMARY — Measurement of total, free, and salivary cortisol has been advocated for the assessment of adrenal function. The results are affected by the following factors:

The assay methodology affects the normal range. Currently available antibody-based assays cross react with non-cortisol steroids and have a higher upper limit of normal than structurally-based assays such as high pressure liquid chromatography.

Changes in CBG and albumin, the binding proteins for cortisol, affect total serum levels, but not free levels in the serum or saliva. These proteins may be substantially reduced in critically ill patients, so that total cortisol values may not reflect adrenal function. Conversely, estrogen-induced increases in CBG may mask low cortisol production.

In individuals with normal sleep-wake cycles, cortisol values are lowest around bedtime, and peak in the early morning. This physiologic difference has been used for diagnostic purposes:

Patients with Cushing's syndrome have elevated late night salivary and serum cortisol values. (See "Establishing the diagnosis of Cushing's syndrome".)

Patients with severe adrenal insufficiency may have low early morning serum cortisol concentrations. If the value is greater than 10 mcg/dL (276 nmol/L), it is unlikely that the patient has clinically important adrenal insufficiency, whereas if it is less than 3 mcg/dL (83 nmol/L), the probability of adrenal insufficiency is high.

DISCLOSURE — The views expressed in this topic are those of the author(s) and do not reflect the official views or policy of the United States Government or its components.

  1. Hawley JM, Owen LJ, Lockhart SJ, et al. Serum Cortisol: An Up-To-Date Assessment of Routine Assay Performance. Clin Chem 2016; 62:1220.
  2. NELSON DH, SAMUELS LT. A method for the determination of 17-hydroxycorticosteroids in blood; 17-hydroxycorticosterone in the peripheral circulation. J Clin Endocrinol Metab 1952; 12:519.
  3. Murphy BE. Some studies of the protein-binding of steroids and their application to the routine micro and ultramicro measurement of various steroids in body fluids by competitive protein-binding radioassay. J Clin Endocrinol Metab 1967; 27:973.
  4. Murphy BE. Non-chromatographic radiotransinassay for cortisol: application to human adult serum, umbilical cord serum, and amniotic fluid. J Clin Endocrinol Metab 1975; 41:1050.
  5. MATTINGLY D. A simple fluorimetric method for the estimation of free 11-hydroxycorticoids in human plasma. J Clin Pathol 1962; 15:374.
  6. Ballard PL, Carter JP, Graham BS, Baxter JD. A radioreceptor assay for evaluation of the plasma glucocorticoid activity of natural and synthetic steroids in man. J Clin Endocrinol Metab 1975; 41:290.
  7. Blair J, Adaway J, Keevil B, Ross R. Salivary cortisol and cortisone in the clinical setting. Curr Opin Endocrinol Diabetes Obes 2017; 24:161.
  8. Guo T, Taylor RL, Singh RJ, Soldin SJ. Simultaneous determination of 12 steroids by isotope dilution liquid chromatography-photospray ionization tandem mass spectrometry. Clin Chim Acta 2006; 372:76.
  9. Taylor RL, Grebe SK, Singh RJ. Quantitative, highly sensitive liquid chromatography-tandem mass spectrometry method for detection of synthetic corticosteroids. Clin Chem 2004; 50:2345.
  10. Gotelli GR, Wall JH, Kabra PM, Marton LJ. Fluorometric liquid-chromatographic determination of serum cortisol. Clin Chem 1981; 27:441.
  11. Gore M, Lester E. Comparison of a fluorimetric method and a competitive protein binding assay kit for the determination of plasma hydroxycorticosteroids. Ann Clin Biochem 1975; 12:160.
  12. Papanicolaou DA, Yanovski JA, Cutler GB Jr, et al. A single midnight serum cortisol measurement distinguishes Cushing's syndrome from pseudo-Cushing states. J Clin Endocrinol Metab 1998; 83:1163.
  13. Bright GM, Darmaun D. Corticosteroid-binding globulin modulates cortisol concentration responses to a given production rate. J Clin Endocrinol Metab 1995; 80:764.
  14. Brien TG. Human corticosteroid binding globulin. Clin Endocrinol (Oxf) 1981; 14:193.
  15. Coolens JL, Van Baelen H, Heyns W. Clinical use of unbound plasma cortisol as calculated from total cortisol and corticosteroid-binding globulin. J Steroid Biochem 1987; 26:197.
  16. Musa BU, Seal US, Doe RP. Elevation of certain plasma proteins in man following estrogen administration: a dose-response relationship. J Clin Endocrinol Metab 1965; 25:1163.
  17. PETERSON RE, NOKES G, CHEN PS Jr, BLACK RL. Estrogens and adrenocortical function in man. J Clin Endocrinol Metab 1960; 20:495.
  18. Aron DC, Tyrrell JB, Fitzgerald PA, et al. Cushing's syndrome: problems in diagnosis. Medicine (Baltimore) 1981; 60:25.
  19. Fernández-Real JM, Grasa M, Casamitjana R, et al. Plasma total and glycosylated corticosteroid-binding globulin levels are associated with insulin secretion. J Clin Endocrinol Metab 1999; 84:3192.
  20. McCann VJ, Fulton TT. Cortisol metabolism in chronic liver disease. J Clin Endocrinol Metab 1975; 40:1038.
  21. Ramirez G, Gomez-Sanchez C, Meikle WA, Jubiz W. Evaluation of the hypothalamic hypophyseal adrenal axis in patients receiving long-term hemodialysis. Arch Intern Med 1982; 142:1448.
  22. Smith SR, Bledsoe T, Chhetri MK. Cortisol metabolism and the pituitary-adrenal axis in adults with protein-calorie malnutrition. J Clin Endocrinol Metab 1975; 40:43.
  23. Franks RC. Diurnal variation of plasma 17-hydroxycorticosteroids in children. J Clin Endocrinol Metab 1967; 27:75.
  24. HILLMAN DA, GIROUD CJ. PLASMA CORTISONE AND CORTISOL LEVELS AT BIRTH AND DURING THE NEONATAL PERIOD. J Clin Endocrinol Metab 1965; 25:243.
  25. Pfohl B, Sherman B, Schlechte J, Stone R. Pituitary-adrenal axis rhythm disturbances in psychiatric depression. Arch Gen Psychiatry 1985; 42:897.
  26. Pfohl B, Sherman B, Schlechte J, Winokur G. Differences in plasma ACTH and cortisol between depressed patients and normal controls. Biol Psychiatry 1985; 20:1055.
  27. Schlechte JA, Coffman T. Plasma free cortisol in depressive illness--a review of findings and clinical implications. Psychiatr Med 1985; 3:23.
  28. Fink RS, Short F, Marjot DH, James VH. Abnormal suppression of plasma cortisol during the intravenous infusion of dexamethasone to alcoholic patients. Clin Endocrinol (Oxf) 1981; 15:97.
  29. Ho JT, Al-Musalhi H, Chapman MJ, et al. Septic shock and sepsis: a comparison of total and free plasma cortisol levels. J Clin Endocrinol Metab 2006; 91:105.
  30. Hamrahian AH, Oseni TS, Arafah BM. Measurements of serum free cortisol in critically ill patients. N Engl J Med 2004; 350:1629.
  31. Migeon CJ, Lawrence B, Bertrand J, Holman GH. In vivo distribution of some 17-hydroxycorticoids between the plasma and red blood cells of man. J Clin Endocrinol Metab 1959; 19:1411.
  32. Newsome HH Jr, Clements AS, Borum EH. The simultaneous assay of cortisol, corticosterone, 11-deoxycortisol, and cortisone in human plasma. J Clin Endocrinol Metab 1972; 34:473.
  33. Robin P, Predine J, Milgrom E. Assay of unbound cortisol in plasma. J Clin Endocrinol Metab 1978; 46:277.
  34. Huang W, Kalhorn TF, Baillie M, et al. Determination of free and total cortisol in plasma and urine by liquid chromatography-tandem mass spectrometry. Ther Drug Monit 2007; 29:215.
  35. Arafah BM, Nishiyama FJ, Tlaygeh H, Hejal R. Measurement of salivary cortisol concentration in the assessment of adrenal function in critically ill subjects: a surrogate marker of the circulating free cortisol. J Clin Endocrinol Metab 2007; 92:2965.
  36. Anderson DC, Hopper BR, Lasley BL, Yen SS. A simple method for the assay of eight steroids in small volumes of plasma. Steroids 1976; 28:179.
  37. New MI, Lorenzen F, Lerner AJ, et al. Genotyping steroid 21-hydroxylase deficiency: hormonal reference data. J Clin Endocrinol Metab 1983; 57:320.
  38. White PC, New MI, Dupont B. Congenital adrenal hyperplasia. (1). N Engl J Med 1987; 316:1519.
  39. McKenna TJ, Moore G, Orth DN, et al. The biosynthesis of androgens in 21-hydroxylase deficiency. In: Adrenal Androgens, Genazzani AR, Thijssen JHH, Siiteri PK (Eds), Raven Press, New York 1980. p.135.
  40. Meikle AW, West SC, Weed JA, Tyler FH. Single dose metyrapone test: 11 beta-hydroxylase inhibition by metyrapone and reduced metyrapone assayed by radioimmunoassay. J Clin Endocrinol Metab 1975; 40:290.
  41. Bertagna C, Orth DN. Clinical and laboratory findings and results of therapy in 58 patients with adrenocortical tumors admitted to a single medical center (1951 to 1978). Am J Med 1981; 71:855.
  42. Walker RF, Riad-Fahmy D, Read GF. Adrenal status assessed by direct radioimmunoassay of cortisol in whole saliva or parotid saliva. Clin Chem 1978; 24:1460.
  43. Umeda T, Hiramatsu R, Iwaoka T, et al. Use of saliva for monitoring unbound free cortisol levels in serum. Clin Chim Acta 1981; 110:245.
  44. Chen YM, Cintrón NM, Whitson PA. Long-term storage of salivary cortisol samples at room temperature. Clin Chem 1992; 38:304.
  45. Laudat MH, Cerdas S, Fournier C, et al. Salivary cortisol measurement: a practical approach to assess pituitary-adrenal function. J Clin Endocrinol Metab 1988; 66:343.
  46. Allolio B, Hoffmann J, Linton EA, et al. Diurnal salivary cortisol patterns during pregnancy and after delivery: relationship to plasma corticotrophin-releasing-hormone. Clin Endocrinol (Oxf) 1990; 33:279.
  47. Raff H, Raff JL, Findling JW. Late-night salivary cortisol as a screening test for Cushing's syndrome. J Clin Endocrinol Metab 1998; 83:2681.
  48. Raff H, Homar PJ, Burns EA. Comparison of two methods for measuring salivary cortisol. Clin Chem 2002; 48:207.
  49. Viera JGH, Noguti KO, Hidal JT, et al. Measurement of saliva cortisol as a method for the evaluation of free serum fraction. Arq Bras Endocrinol Metab 1984; 28:8.
  50. Castro M, Elias PC, Quidute AR, et al. Out-patient screening for Cushing's syndrome: the sensitivity of the combination of circadian rhythm and overnight dexamethasone suppression salivary cortisol tests. J Clin Endocrinol Metab 1999; 84:878.
  51. Liu H, Bravata DM, Cabaccan J, et al. Elevated late-night salivary cortisol levels in elderly male type 2 diabetic veterans. Clin Endocrinol (Oxf) 2005; 63:642.
  52. Baid SK, Sinaii N, Wade M, et al. Radioimmunoassay and tandem mass spectrometry measurement of bedtime salivary cortisol levels: a comparison of assays to establish hypercortisolism. J Clin Endocrinol Metab 2007; 92:3102.
  53. Evans PJ, Peters JR, Dyas J, et al. Salivary cortisol levels in true and apparent hypercortisolism. Clin Endocrinol (Oxf) 1984; 20:709.
  54. Hermus AR, Pieters GF, Borm GF, et al. Unpredictable hypersecretion of cortisol in Cushing's disease: detection by daily salivary cortisol measurements. Acta Endocrinol (Copenh) 1993; 128:428.
  55. Mosnier-Pudar H, Thomopoulos P, Bertagna X, et al. Long-distance and long-term follow-up of a patient with intermittent Cushing's disease by salivary cortisol measurements. Eur J Endocrinol 1995; 133:313.
  56. Papanicolaou DA, Mullen N, Kyrou I, Nieman LK. Nighttime salivary cortisol: a useful test for the diagnosis of Cushing's syndrome. J Clin Endocrinol Metab 2002; 87:4515.
Topic 161 Version 8.0

References