Acromegaly laboratory findings
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief:
Overview
- An elevated/reduced concentration of serum/blood/urinary/CSF/other [lab test] is diagnostic of [disease name].
- Laboratory findings consistent with the diagnosis of [disease name] include [abnormal test 1], [abnormal test 2], and [abnormal test 3].
- [Test] is usually normal among patients with [disease name].
- Some patients with [disease name] may have elevated/reduced concentration of [test], which is usually suggestive of [progression/complication].
OR
- There are no diagnostic laboratory findings associated with [disease name].
Laboratory Findings
- Laboratory findings consistent with the diagnosis of acromegaly include:
- Insulin Growth Factor 1 (IGF-1) level:[1][2]
- IGF-1 level measurement is one of the best laboratory test to diagnose acromegaly. IGF-1 level is elevated in all patients with acromegaly.
- IGF-1 measurement has been recommended in the patients with acromegaly clinical features to measure the level of IGF-1.
- IGF-1 measurement has been recommended also to measure the IGF-1 in the patients who do not have the typical acral features but have associated conditions like sleep apnea and carpal tunnel syndrome.
- IGF-1 level is measured also in the patients with only pituitary adenoma to exclude acromegaly.
- IGF-1 is affected by some factors as the age of the patient, genes, sex hormones and steroids. Although it is one of the best lab tests to diagnose acromegaly, it is not used alone in the diagnosis.[3]
- Insulin Growth Factor 1 (IGF-1) level:[1][2]
Labs
If acromegaly is suspected, a doctor must measure the GH level in a person’s blood to determine if it is elevated. However, a single measurement of an elevated blood GH level is not enough to diagnose acromegaly: Because GH is secreted by the pituitary in impulses, or spurts, its concentration in the blood can vary widely from minute to minute. At a given moment, a person with acromegaly may have a normal GH level, whereas a GH level in a healthy person may even be five times higher.
More accurate information is obtained when GH is measured under conditions that normally suppress GH secretion. Health care professionals often use the oral glucose tolerance test to diagnose acromegaly because drinking 75 to 100 grams of glucose solution lowers blood GH levels to less than 1 nanogram per milliliter (ng/ml) in healthy people. In people with GH overproduction, this suppression does not occur. The oral glucose tolerance test is a highly reliable method for confirming a diagnosis of acromegaly.
Physicians also can measure IGF-I levels, which increase as GH levels go up, in people with suspected acromegaly. Because IGF-I levels are much more stable than GH levels over the course of the day, they are often a more practical and reliable screening measure. Elevated IGF-I levels almost always indicate acromegaly. However, a pregnant woman’s IGF-I levels are two to three times higher than normal. In addition, physicians must be aware that IGF-I levels decline with age and may also be abnormally low in people with poorly controlled diabetes or liver or kidney disease.
References
- ↑ Katznelson L, Laws ER, Melmed S, Molitch ME, Murad MH, Utz A; et al. (2014). "Acromegaly: an endocrine society clinical practice guideline". J Clin Endocrinol Metab. 99 (11): 3933–51. doi:10.1210/jc.2014-2700. PMID 25356808.
- ↑ Clemmons DR, Van Wyk JJ, Ridgway EC, Kliman B, Kjellberg RN, Underwood LE (1979). "Evaluation of acromegaly by radioimmunoassay of somatomedin-C". N Engl J Med. 301 (21): 1138–42. doi:10.1056/NEJM197911223012102. PMID 492275.
- ↑ Clemmons DR (2006). "Clinical utility of measurements of insulin-like growth factor 1". Nat Clin Pract Endocrinol Metab. 2 (8): 436–46. doi:10.1038/ncpendmet0244. PMID 16932333.