Trang 6 viiContentsPart I Dynamic Tests in Pituitary/Adrenal Disorders1 ACTH Stimulation Test for Adrenal Insufficiency with Total Cortisol Levels .... Ergin et al., The Cleveland Clinic
Dynamic Tests in Thyroid Disorders
Dynamic Tests in Pituitary/Adrenal
ACTH Stimulation Test for Adrenal
Insufficiency with Total Cortisol Levels © Springer International Publishing Switzerland 2015
A B Ergin et al., The Cleveland Clinic Manual of Dynamic Endocrine Testing,
Indication: This test is performed to determine whether the adrenal glands can respond normally to ACTH by producing cortisol.
Preparation: Patients should be off glucocorticoids that potentially inter- fere with the cortisol assay (hydrocortisone, prednisone) for
24 h pretesting Dexamethasone may be used.
Materials Needed: Three (3) gold top tubes labeled as baseline, 30, and/or
60 min Cortrosyn 250 mcg Syringes/needles
Assay for Cortisol: Chemiluminescence immunoassay (CLIA).
Precautions: Cosyntropin is category C for pregnancy.
In a typical response to cortrosyn administration, a peak stimulated cortisol level exceeding 18 mcg/dl at 30 minutes is expected Most patients tend to exhibit elevated cortisol levels at the 60-minute mark compared to their 30-minute readings after receiving 250 mcg of cortrosyn Thus, establishing a cut-off value for cortisol response is essential for accurate interpretation.
18 mcg/dL at 60 min may be associated with an increased false positive result.
• Taking oral estrogen may result in elevation of the total cortisol level due to increased corticosteroid binding globulin [3].
• Patients with albumin < 2.5 gr/dL may have a low cortisol level [4].
• Sensitivity for the test is limited in secondary adrenal insufficiency Specificity is > 95 %, thus a positive cosyntropin test result substantially increases the likelihood that the patient has secondary adrenal insufficiency [5].
1 ACTH Stimulation Test for Adrenal Insufficiency with Total Cortisol Levels
1 Draw blood sample for baseline serum cortisol.
3 At 30 and/or 60 min, draw blood samples for serum cortisol.
RN performing the procedure: Additional orders by physician: _
6 1 ACTH Stimulation Test for Adrenal Insufficiency with Total Cortisol Levels
1 Grinspoon SK, Biller BM Clinical review 62: laboratory assessment of adrenal insufficiency
2 May ME, Carey RM Rapid adrenocorticotropic hormone test in practice Retrospective review Am J Med 1985;79(6):679–84.
3 Klose M, Lange M, Rasmussen AK, et al Factors influencing the adrenocorticotropin test: Role of contemporary cortisol assays, body composition, and oral contraceptive agents J Clini Endocrinol Metab 2007;92(4):1326–33.
4 Hamrahian AH, Oseni TS, Arafah BM Measurements of serum free cortisol in critically ill patients N Engl J Med 2004;350(16):1629–38.
5 Dorin RI, Qualls CR, Crapo LM Diagnosis of adrenal insufficiency Ann Intern Med 2003;139(3):194–204.
ACTH Stimulation Test for Adrenal
Insufficiency with Free Cortisol Levels © Springer International Publishing Switzerland 2015
A B Ergin et al., The Cleveland Clinic Manual of Dynamic Endocrine Testing,
The adrenal response test evaluates the adrenal glands' ability to produce free cortisol in response to ACTH stimulation This test is especially useful for patients with albumin levels below 2.5 mg/dL or low CBG levels.
Preparation: Patients should be off glucocorticoids that poten- tially interfere with the cortisol assay (hydro- cortisone, prednisone) for 24 h pretesting Dexamethasone may be used.
Materials Needed: Three (3) gold top tubes labeled as baseline, 30, and/or 60 min
Assay for Cortisol: Electrochemiluminescence immunoassay (ECLIA).
Precautions: Cosyntropin is category C for pregnancy.
A normal response to cosyntropin administration is indicated by a peak stimulated cortisol level greater than 1.2 mcg/dl at either 30 or 60 minutes Typically, subjects demonstrate elevated cortisol levels at the 60-minute mark compared to the 30-minute measurement after receiving 250 mcg of cosyntropin.
8 2 ACTH Stimulation Test for Adrenal Insufficiency with Free Cortisol Levels
The established cut-off value may not be applicable to patients in the ICU, indicating a need for further research to determine suitable levels for this population Additionally, the advantages of glucocorticoid therapy in septic shock patients may extend beyond just adrenal function status.
• Free cortisol index (FCI) may be used as an alternative to this dynamic test, if free cortisol assay is not available.
• FCI: Total cortisol (nmol/L)/CBG (mg/dl) < 12 suggests adrenal insufficiency
[5] Total cortisol should be measured in the morning between 8–10 am.
2 ACTH Stimulation Test for Adrenal Insufficiency with Free Cortisol Levels
1 Draw blood sample for baseline serum free cortisol.
3 At 30 and/or 60 min, draw blood samples for serum cortisol.
10 2 ACTH Stimulation Test for Adrenal Insufficiency with Free Cortisol Levels
1 Hamrahian AH, Oseni TS, Arafah BM Measurements of serum free cortisol in critically ill patients N Engl J Med 2004;350(16):1629–38.
2 Tan T, Chang L, Woodward A, McWhinney B, Galligan J, Macdonald GA, et al Characterizing adrenal function using directly measured plasma free cortisol in stable severe liver disease J Hepatol 2010;53(5):841–8.
3 Lewis JG, Bagley CJ, Elder PA, Bachmann AW, Torpy DJ Plasma-free cortisol fraction reflects levels of functioning corticosteroid-binding globulin Clinica Chimica Acta 2005;359 (1–2):189–94.
4 Vogeser M, Briegel J, Zachoval R Dialyzable free cortisol after stimulation with synacthen Clin Biochem 2002;35(7):539–43.
A study by Le Roux et al (2003) published in the Journal of Clinical Endocrinology and Metabolism highlights that the free cortisol index is a more effective measure than total serum cortisol for assessing hypothalamic-pituitary-adrenal (HPA) status in surgical patients This finding underscores the importance of using the free cortisol index for more accurate evaluations of HPA function in clinical settings.
ACTH Stimulation Test for Late Onset
(Nonclassic) 21-Hydroxylase Deficiency © Springer International Publishing Switzerland 2015
A B Ergin et al., The Cleveland Clinic Manual of Dynamic Endocrine Testing,
Indication: To evaluate for androgen excess in diagnosing non- classic CYP21A2 deficiency If Basal 17-hydroxypro- gesterone (17 OHP) < 2 ng/ml, diagnosis is unlikely and ACTH stimulation may not be necessary [1, 2].
For optimal testing of women, it is advised to conduct assessments during the early follicular phase of the menstrual cycle To ensure accurate results, it is recommended to withhold glucocorticoids for 24 hours prior to testing, as they may influence the levels of 17 OH progesterone.
Materials Needed: Two (2) gold top tubes labeled as baseline and 60 minutes Cortrosyn 250 mcg Syringes/needles
Assay for 17 OHP: Radioimmunoassay (RIA).
Interpretation: With late onset 21-hydroxylase deficiency, the abso- lute value of 17-hydroxyprogesterone at 60 min sam- ple is > 10 ng/dl [2, 3].
• Baseline androgen levels return to baseline after 8 weeks of discontinuation of oral contraceptive pills (OCP) [4].
• There is not enough data in regards to the effect of OCP on 17 OHP levels after ACTH stimulation.
3 ACTH Stimulation Test for Late Onset (Nonclassic) 21-Hydroxylase Deficiency 13
1 Obtain baseline blood sample for (17 OHP) and cortisol.
3 At 60 min, obtain sample for (17 OHP) and cortisol.
RN performing the procedure: _ Additional orders by physician:
14 3 ACTH Stimulation Test for Late Onset (Nonclassic) 21-Hydroxylase Deficiency
1 Azziz R, Zacur HA 21-hydroxylase deficiency in female hyperandrogenism: screening and diagnosis J Clin Endocrinol Metab 1989;69(3):577–84.
2 Azziz R, Dewailly D, Owerbach D Clinical review 56: nonclassic adrenal hyperplasia: current concepts J Clin Endocrinol Metabo 1994;78(4):810–5.
3 New MI, Lorenzen F, Lerner AJ, et al Genotyping steroid 21-hydroxylase deficiency: hormonal reference data J Clini Endocrinol Metabo 1983;57(2):320–6.
A prospective study by Sanchez et al (2007) investigated the time required for androgens and sex hormone-binding globulin (SHBG) to return to baseline levels following the discontinuation of oral contraceptives in women with polycystic ovary syndrome (PCOS) The findings contribute valuable insights into hormonal recovery patterns in this population, highlighting the implications for managing PCOS symptoms post-contraceptive use.
Metyrapone Stimulation Test © Springer International Publishing Switzerland 2015
A B Ergin et al., The Cleveland Clinic Manual of Dynamic Endocrine Testing,
Indication: To evaluate HPA axis integrity It is a sensitive alternative test to insulin tolerance test (ITT) in order to evaluate the adrenocorticotrophic hor- mone (ACTH) reserve.
Preparation: The patient may eat and drink normally prior to the test.
Metyrapone po (30 mg/kg body weight, or 2 g for < 70 kg, 2.5 g for 70 to 90 kg, and 3 g for
Assay for Cortisol and ACTH: Chemiluminescence Assay (CLIA).
Assay for 11 DOC: LC-MS/MS.
Precautions: Hypotension, nausea, vomiting, abdominal discomfort or cramping, and musculoskeletal pain in patients with adrenal insufficiency may happen Metyrapone can also cause dizziness, sedation, and allergic rash.
Lavender top tube on ice
Note: Separate plasma from cells ASAP
Metyrapone inhibits the enzyme CYP11B1, which is responsible for converting 11-deoxycortisol to cortisol, resulting in a swift decrease in cortisol levels and an increase in ACTH stimulation.
1 A normal response to the overnight single- dose test consists of [1–3]:
• A serum cortisol concentration at 8 AM of less than 5 àg/dL (138 nmol/L) confirms adequate metyrapone blockade.
• An 8 AM serum 11-DOC concentration
Insufficient serum 11-DOC concentration exceeding 7 mcg/dL, despite serum cortisol levels above 5 mcg/dL, may indicate inadequate blockage of 11 beta hydroxylase In these cases, it is recommended to retest after administering a higher dosage of metyrapone.
• The metyrapone test is the most sensitive method to detect partial defects in pituitary ACTH secretion [1, 3].
Conventional immunoassays for measuring cortisol levels may yield falsely elevated results due to interference from increased levels of 11-deoxycortisol caused by metyrapone For the most accurate results, liquid chromatography tandem mass spectrometry steroid assays are recommended.
The metyrapone test is not recommended for assessing primary adrenal insufficiency Instead, healthcare providers should prioritize measuring morning serum cortisol, plasma ACTH levels, or conducting an ACTH stimulation test for accurate evaluation.
1 Patient ingests metyrapone (30 mg/kg body weight, or 2 g for
< 70 kg, 2.5 g for 70–90 kg, and 3 g for > 90 kg body weight at midnight/bedtime with a glass of milk or a small snack.
2 Serum 11-deoxycortisol, cortisol, and plasma ACTH are mea- sured between 7:30 and 9:30 AM the next morning [1, 2].
1 Fiad TM, Kirby JM, Cunningham SK, McKenna TJ The overnight single‐dose metyrapone test is a simple and reliable index of the hypothalamic‐pituitary‐adrenal axis Clin Endocrinol (Oxf) 1994;40(5):603–9.
2 Steiner H, Bọhr V, Exner P, Oelkers P Pituitary function tests: comparison of ACTH and 11-de- oxy-cortisol responses in the metyrapone test and with the insulin hypoglycemia test Exp Clinic Endocrinol Diabetes 1994;102(01):33–8.
A study by Gibney et al (2008) presents a straightforward and economical method for evaluating pituitary adrenocorticotropin and growth hormone reserves This approach combines the overnight metyrapone test with insulin-like growth factor-I standard deviation scores, offering an effective assessment tool for clinicians The findings are detailed in the Journal of Clinical Endocrinology and Metabolism, emphasizing the utility of this combined testing method in clinical practice.
4 Owen LJ, Halsall DJ, Keevil BG Cortisol measurement in patients receiving metyrapone ther- apy Ann Clin Biochem 2010;47(6):573–5.
Two Day Low Dose Dexamethasone
Suppression Test © Springer International Publishing Switzerland 2015
A B Ergin et al., The Cleveland Clinic Manual of Dynamic Endocrine Testing,
To evaluate cortisol suppressibility in patients with inconclusive screening tests, such as the overnight 1 mg dexamethasone suppression test, 24-hour urinary free cortisol measurement, and late-night salivary cortisol assessment, is essential for accurate diagnosis and treatment planning.
Materials Needed: Eight dexamethasone 0.5 mg tablets
One gold top tube for cortisol
Assay for Cortisol: Chemiluminescence Immunoassay (CLIA).
Interpretation: Serum cortisol concentration > 1.4–1.8 àg/dl after 2 day low dose dex is strongly suggestive of Cushing’s syndrome [1].
• Use of the 2 mg 2-day test has greater specificity at high sensitivity compared to the 1 mg overnight test However, it requires more patience on the part of the patient [2, 3].
We advise against using 24-hour urine cortisol measurement in the 2 mg dexamethasone suppression test (DST), as serum cortisol concentration assessment during the low-dose dexamethasone test is more straightforward and dependable than urinary steroid measurements.
• Do not use this test if the patient is on estrogens which increase cortisol binding globulin (CBG) and falsely elevate cortisol levels [4].
Certain drugs, including phenytoin, phenobarbital, carbamazepine, rifampicin, and alcohol, can enhance the hepatic enzymatic clearance of dexamethasone via CYP 3A4 This interaction leads to decreased plasma concentrations of dexamethasone, potentially resulting in false positive test outcomes.
20 5 Two Day Low Dose Dexamethasone Suppression Test
Dynamic Tests in Glucose Metabolism/Pancreas Disorders
Dynamic Tests in Thyroid Disorders
Thyroid Cancer Follow-Up: Withdrawal
Protocol © Springer International Publishing Switzerland 2015
A B Ergin et al., The Cleveland Clinic Manual of Dynamic Endocrine Testing,
Day Date What to Do
0 Day and Date Have baseline TSH and Thyroglobulin drawn if not done in the past 60 days Stop L-thyroxine medication beginning on day 0
7 Day and Date One week after stopping L-thyroxine, begin Cytomel 25 or 37.5 mcg per day (Circle one dose) for 2 weeks
21 Day and Date Stop Cytomel
28 Day and Date Start low Iodine diet
35 Day and Date Have TSH, Thyroglobulin lab work
37 Day and Date Start collecting (24 h urine for iodine/creatinine) from 8 a.m to 8 a.m (next day) take it to lab prior to appointment
38 Day and Date Report to nuclear medicine for tracer dose of 131 I in preparation for neck scan next day
A 40-day and date report is required for a whole-body nuclear medicine scan, scheduled for the morning, 48 hours after tracer dose ingestion If deemed necessary by your endocrinologist, you may receive a radioactive iodine (RAI) treatment dose on this day Additionally, if you are a female under the age of 55, it is essential to undergo a pregnancy test beforehand.
Day and Date Report to nuclear medicine for total body scan if you have received radioactive iodine treatment dose
Start LOW IODINE DIET Date:
Thyroid Cancer Follow-Up: Thyrogen
Injection with No Scan © Springer International Publishing Switzerland 2015
A B Ergin et al., The Cleveland Clinic Manual of Dynamic Endocrine Testing,
Day Date What to do
1 Day and date Have labs (thyroglobulin) drawn
If female of age 55 or under, have a pregnancy test done prior to thyrogen injection
First thyrogen injection given by the nurse
2 Day and date Second thyrogen injection given by the nurse
5 Day and date Have labs (thyroglobulin) drawn at main campus or satellite
Name and Signature, RN: _Name and Signature, MD: _
Thyroid Cancer Follow-Up: Thyrogen Injection with Scan With/Without Treatment © Springer International Publishing Switzerland 2015
A B Ergin et al., The Cleveland Clinic Manual of Dynamic Endocrine Testing,
Day Date and time What to do
− 14 Day and date Start with low-iodine diet Continue this diet until after you have your blood work done on Day 5
1 Day and date Have labs (TSH and thyroglobulin) drawn in the morning prior to thyrogen injection
If female of age 55 or under, have a pregnancy test done prior to thyrogen injection
First thyrogen injection given by nurse in the morning Come back tomorrow for the second thyrogen injection
2 Day and date Second thyrogen injection given by nurse in the morning
Report to nuclear medicine for a radioactive iodine (RAI) tracer dose in the afternoon
3 Day and date Report to nuclear edicine for a whole body scan in the morning
(48 h after tracer dose ingestion) You may receive RAI treatment dose on this day, if indicated as per your endocrinologist If female age is < 55, have a pregnancy test done prior
5 Day and date Have labs (thyroglobulin) drawn 72 h after you had your injections
You may stop your low-iodine diet after your blood work
Name and Signature, RN: Name and Signature, MD:
Reconstitution, Preparation, and Administration of THYROGEN (Obtained from Prescribing Information)
The supplied lyophilized powder must be reconstituted with sterile water for injec- tion THYROGEN should be prepared and administered in the following manner:
• Add 1.2 mL of sterile water for injection to the vial containing the THYROGEN- lyophilized powder.
• Swirl the contents of the vial until all materials are dissolved Do not shake the solution The reconstituted THYROGEN solution has a concentration of 0.9 mg of thyrotropin alfa per mL.
Before administering the reconstituted THYROGEN solution, visually inspect it for any particulate matter or discoloration The solution should appear clear and colorless; do not use it if it is cloudy or contains any particles.
To administer THYROGEN, withdraw 1 mL of the reconstituted solution containing 0.9 mg of thyrotropin alfa and inject it intramuscularly into the buttocks It is essential to inject the reconstituted solution within 3 hours unless it has been refrigerated, in which case it can be stored for up to 24 hours.
• Discard unused portions Do not mix with other substances.
Levothyroxine Absorption Test © Springer International Publishing Switzerland 2015
A B Ergin et al., The Cleveland Clinic Manual of Dynamic Endocrine Testing,
Indication: To assess poor oral absorption of levothyroxine (LT4), and assist the clinician in differentiating true malabsorption from pseudomalabsorption (patient nonadherence).
Materials Needed: Hep-lock/syringes/needle
1000 mcg of LT4 Blood tubes for total or freeT4 measurement
Precautions: Supervise patient continuously during the procedure.
Interpretation: Absorption is calculated by using the following formula [1]:
Volume of distribution (Vd) in deciliters: 4.42 × body mass index [1].
More than 60–80 % absorption is considered normal and rules out levothyroxine malabsorption [2, 3].
4absorption peak Total freeT4 vd dL administered
Biological Causes of Levothyroxine Malabsorption or change in metabolism or requirement [4]
Liver diseases such as cirrhosis
• Before proceeding with this test, the biological causes of levothyroxine malab- sorption should be evaluated as listed below.
• Obesity may cause overestimation of absorption.
• This test is not a well-established test in clinical practice The value of this test should be weighed against risks and cost in each individual patient.
1 Perform the test after an overnight fast.
3 Insert hep-lock and flush with 3–10 ml of normal saline as necessary.
4 Have patient ingest 1000 mcg of levothyroxine.
5 Draw blood for total T4 levels at baseline before ingestion of
6 Draw blood for total T4 levels hourly for 5 h.LT4.
7 Monitor BP and heart rate hourly.
8 Document the dose and time of LT4 given and also document the lab results with timings.
Dose, time and date of LT4 given- Dose: Time: Date: Results Baseline Time 60 min 120 min 180 min 240 min 300 minTT4
1 Singh N, Weisler SL, Hershman JM The acute effect of calcium carbonate on the intestinal absorption of levothyroxine Thyroid 2001;11(10):967–71.
2 Fish LH, Schwartz HL, Cavanaugh J, Steffes MW, Bantle JP, Oppenheimer JH Replacement dose, metabolism, and bioavailability of levothyroxine in the treatment of hypothyroidism N Engl J Med 1987;316(13):764–70.
3 Wenzel KW, Kirschsieper HE Aspects of the absorption of oral L-thyroxine in normal man Metab Clin Exp 1977;26(1):1–8.
4 Lips D, Van Reisen M, Voigt V, Venekamp W Diagnosis and treatment of levothyroxine pseu- domalabsorption Neth J Med 2004;62(4):114–8.
Invasive Dynamic Endocrine Testing
Dynamic Tests in Glucose Metabolism/
Seventy Two Hours Fast for Insulinoma © Springer International Publishing Switzerland 2015
A B Ergin et al., The Cleveland Clinic Manual of Dynamic Endocrine Testing,
Indication: To confirm and determine the cause of suspected spontane- ous hypoglycemia.
Contraindication: Pregnancy, liver or kidney failure, unstable angina.
Preparation: No special preparation is needed Patient can have breakfast on the day of testing if hypoglycemia develops frequently.
Materials Needed: Blood tubes in sufficient amount for testing should be ready at bedside:
For optimal testing, utilize a maximum of three tubes: a gold top tube for insulin, pro-insulin, and C-peptide; a grey top tube for fasting blood glucose (BG); and a green top tube for beta-hydroxybutyrate.
Insulin: Gold top tube, 1 ml Methodology: chemilumines- cence immunoassay
Pro-insulin gold top tube, 1 ml Assay: methodology: che- miluminescence immunoassay transport: centrifuge, aliquot, and freeze (keep in ice until delivered to the lab)
C-Peptide: Gold top tube, 1 ml Methodology: chemilumi- nescence immunoassay
Fasting glucose grey-top tube, 1 ml Methodology: glucose hexokinase
Beta hydroxybutyrate green-top tube, 1 ml Methodology: enzymatic
23 Seventy Two Hours Fast for Insulinoma 94
Precautions: All patients must be warned that they will be fasting, and unable to leave the clinic/ward unaccompanied during the test before starting.
Have D50 and glucagon ampule ready in case of emergency.
Interpretation: See table [1] below for interpretation.
Accurate labeling of blood samples and laboratory slips, especially with the precise time, is crucial for effective result interpretation Additionally, documenting this information on a flow sheet ensures that all necessary details are preserved for future analysis.
• Young, lean, healthy women may have plasma glucose concentrations in the range of 40 mg/dL (2.2 mmol/L) or even lower after prolonged periods of fasting
A low plasma glucose level is essential for diagnosing hypoglycemia, but it alone does not confirm the condition It is crucial to continue testing as outlined in the procedure, without interruption Additionally, thorough questioning and repeated assessments for subtle symptoms or signs of hypoglycemia should be performed when a patient's plasma glucose is approaching or within the hypoglycemic range.
The established diagnostic parameters demonstrate varying sensitivity and specificity levels: Insulin (≥ 3 μU/ml) shows 93% sensitivity and 95% specificity; C-peptide (≥ 0.2 nmol/ml) has 100% sensitivity and 60% specificity; proinsulin (≥ 5 pmol/L) exhibits 100% sensitivity and 68% specificity; BHOB (≤ 2.7 mmol/L) presents both sensitivity and specificity at 100%; and plasma glucose response to intravenous glucagon (≥ 25 mg/dl) indicates 91% sensitivity and 95% specificity.
• The specificity of these parameters was improved when compared with normal patients whose plasma glucose at the end of a prolonged fast was 50 mg/dl or
23 Seventy Two Hours Fast for Insulinoma 95 less: insulin, 100 %; C-peptide, 78 %; proinsulin, 78 %; and glucose response to glucagon, 100 % [3].
Approximately 6% of insulinomas manifest as postprandial hypoglycemia, a condition that can also be seen in other disorders like nesidioblastosis The mixed meal test may be useful in assessing patients experiencing these symptoms.
23 Seventy Two Hours Fast for Insulinoma 97
1 Date the last ingestion of calories.
2 Document the baseline vital signs.
3 Stop all foods and drinks except calorie free and caffeine free beverages and water.
4 Ensure that the patient is active during waking hours.
6 Flush heplock with 3–10 cc ml normal saline as needed.
7 Draw blood for baseline labs for 5 tests: insulin, pro-insulin,
C-peptide, fasting glucose, beta hydroxybutyrate.
8 Check finger stick blood sugar every 2 h until BG is 60 mg/dl or less.
9 Check finger stick blood sugar every 1 h after BG is 60 mg/dl or less.
When blood glucose levels drop below 60 mg/dl, send stat blood samples for five specific tests: insulin, glucose, c-peptide, and beta-hydroxybutyrate Continue to collect samples every hour, but ensure that analysis is performed only on samples where plasma glucose concentration is below 45 mg/dl (2.5 mmol/L).
It's crucial to avoid making the decision to end a fast solely based on a fingerstick blood glucose (BG) reading In cases of severe symptoms that require urgent treatment, ensure that samples are collected for all necessary tests before administering carbohydrates.
Recommend to draw blood twice a day regardless of BG levels In some cases the trend in the levels can help clini- cians with interpretation,
• plasma glucose concentration is ≤ 45 mg/dL (2.5 mmol/L) in plasma (not in fingestick) in an asymtopmatic patient after careful evaluation (see caveats) or
• patient has symptoms or signs of hypoglycemia when BG is ≤ 45 mg/dL in plasma or
• plasma glucose concentration is less than 55 mg/dL
(3 mmol/L) if Whipple’s triad was documented on a prior occasion or
23 Seventy Two Hours Fast for Insulinoma 98
After ending the test send blood samples STAT for the following:
Insulin, pro-insulin, C-peptide, fasting glucose, beta hy- droxybutyrate, and hypoglycemia panel that include sulfo- nylurea screen and other insulin secretagogues.
12 Give 1 mg glucagon intravenously and recheck plasma glucose
10, 20, and 30 min later Patient should be then fed right away after last blood draw.
23 Seventy Two Hours Fast for Insulinoma 99
Glucose (Time) e.g 45 (3:12Symptoms Y/NInsulinC-peptideProinsulin
BG increase after glucagon > 25mg/dl Y/N
23 Seventy Two Hours Fast for Insulinoma 100
1 Cryer PE, Axelrod L, Grossman AB, Heller SR, Montori VM, Seaquist ER Evaluation and management of adult hypoglycemic disorders: an endocrine society clinical practice guideline
2 Merimee TJ, Fineberg SE Homeostasis during fasting II Hormone substrate differences between men and women J Clin Endocrinol Metab 1973;37(5):698–702.
3 Placzkowski KA, Vella A, Thompson GB, et al Secular trends in the presentation and management of functioning insulinoma at the mayo clinic, 1987–2007 J Clin Endocrinol Metab 2009;94(4):1069–73.
Glucagon Stimulation © Springer International Publishing Switzerland 2015
A B Ergin et al., The Cleveland Clinic Manual of Dynamic Endocrine Testing,
Indication: Assessment of beta cell reserve.
Contraindication: Patients with type 1 diabetes mellitus.
Preparation [1:] NPO except water after midnight and during the test.
Ten hours after the last dose of short-acting or intermedi- ate-acting insulin, metformin or thiazolidinedione.
At least 24 h after a dose of sulfonylurea or long-acting insulin (glargine or detemir).
Materials Needed: Three gold top tubes, glucagon
Assay for C-peptide: Chemiluminescence immunoassay.
Beta cell functional reserve is considered preserved when the peak C-peptide response to glucagon is at least 1.5 ng/dL (0.5 nmol/L) or when the fasting C-peptide concentration is at least 1 ng/dL (0.33 nmol/L) Conversely, it is deemed absent if the glucagon-stimulated or fasting C-peptide levels fall below these thresholds Therefore, patients lacking preserved beta cell function according to these criteria should not attempt insulin withdrawal.
The cut-points for human C-peptide, determined through radioimmunoassay (RIA), effectively predict beta cell function and glycemic control over one year However, these standards have not yet been established for newer C-peptide immunoassays.
• Measurement of beta cell antibodies also helps in understanding underlying pa- thology although immediate insulin dependence can be more sharply estimated by measurement of basal or stimulated C-peptide levels.
In patients with diabetic ketoacidosis (DKA) exhibiting the typical type 1 diabetes phenotype, characterized by youth and low body weight, measuring C-peptide levels may be unnecessary It is essential to continue insulin treatment for these individuals.
1 Ensure patient is fasting from midnight.
2 Weigh patient and document it.
3 Insert intravenous cannula (hep-lock) for intravenous access between 7:30–8 A.M.
5 Administer glucagon intravenously 1 mg Confirm the medica- tion doses with physician.
6 Obtain blood samples for C-peptide 5 and 10 min after the glu- cagon infusion.
Glucagon stim test Time C-peptide
Maldonado et al (2003) conducted a comprehensive study on ketosis-prone diabetes, exploring its heterogeneous nature through immunogenetic and β-cell functional classifications Their prospective analysis revealed significant clinical outcomes, enhancing the understanding of this complex syndrome The findings underscore the importance of individualized approaches in managing ketosis-prone diabetes.
2 Balasubramanyam A, Garza G, Rodriguez L, et al Accuracy and predictive value of classifica- tion schemes for ketosis-prone diabetes Diabetes Care 2006;29(12):2575–9.
3 Maldonado M, D’Amico S, Otiniano M, Balasubramanyam A, Rodriguez L, Cuevas E Predic- tors of glycaemic control in indigent patients presenting with diabetic ketoacidosis Diabetes Obes Metab 2005;7(3):282–9.
Mixed Meal Hypoglycemia Test © Springer International Publishing Switzerland 2015
A B Ergin et al., The Cleveland Clinic Manual of Dynamic Endocrine Testing,
Indication: Patients with suspected postprandial hypoglycemia.
Materials needed: Ensure plus high protein drink (6 ml/kg with max dose of
360 ml) Blood tubes in sufficient amount for testing should be ready at bedside:
Maximum three tubes for one set of testing: One gold top tube for insulin, pro-insulin and c-peptide, grey top tube for fasting
BG, and green top tube for beta-hydroxybutyrate.
Insulin: gold top tube, methodology: chemiluminescence immunoassay
Pro-insulin gold top tube, methodology: Chemiluminescence immunoassay, transport: centrifuge, aliquot and freeze (keep on ice until delivered to the lab) C-Peptide: gold top tube, methodology: chemiluminescence immunoassay
Fasting glucose: grey top tube, Methodology Glucose hexokinase
Beta hydroxybutyrate: green top tube Methodology Enzymatic
Precautions: Have D50 and some fruit juice ready in case of emergency.
The interpretation standards for the mixed-meal test remain undefined, with current clinical practice relying on criteria originally established for fasting conditions in insulinoma cases For detailed interpretation, refer to Table 1.
If a patient is symptomatic and blood glucose is normal, diag- nosis of postprandial syndrome can be made.
The oral glucose tolerance test is not suitable for assessing suspected postprandial hypoglycemia, as normal, asymptomatic individuals may experience a drop in blood glucose levels into the hypoglycemic range after consuming 100 g of glucose.
Postprandial (reactive) hypoglycemia refers to low blood sugar levels occurring after meals, but it is important to note that it is not a formal diagnosis Once biochemical evidence of postprandial hypoglycemia is established, identifying the underlying cause is essential Blood samples should only be analyzed when plasma glucose levels fall below 45 mg/dl (2.5 mmol/l).
Table 1 outlines the findings observed during fasting or after a mixed meal in healthy individuals who exhibit no symptoms despite having relatively low plasma glucose levels, indicating that Whipple’s triad is not present Additionally, it includes data on individuals experiencing hyperinsulinemic or IGF-mediated hypoglycemia, as well as those with hypoglycemia resulting from other mechanisms.
1 Perform the test after an overnight fast.
3 Have the patient drink ensure plus high protein drink (6 ml/kg with max dose of 360 ml).