Causes of low IGF-1 in patients with acromegaly<\/h2>\n
In normal physiology, the production of IGF-1 (both hepatic and extra-hepatic) sites is facilitated by thyroxine, testosterone, insulin, and estrogen (low levels). Conversely, IGF-1 production is inhibited by inflammatory cytokines. When the clinical features do not match biochemical testing, these conditions should be considered and excluded.<\/p>\n
- \n
- Uncontrolled diabetes mellitus<\/a><\/li>\n
- Hypothyroidism (both primary and secondary hypothyroidism)<\/li>\n
- Male Hypogonadism<\/a><\/li>\n
- Chronic liver disease<\/li>\n
- Chronic renal failure<\/li>\n
- Malnutrition<\/li>\n
- Systemic illness<\/li>\n
- Oral estrogen therapy<\/li>\n<\/ul>\n
Causes of elevated IGF-1 without acromegaly<\/h2>\n
- \n
- Preclinical disease (acromegaly)<\/li>\n
- Hyperthyroidism<\/li>\n
- Immediately after surgery (for acromegaly). Due to the long-circulating half-life of IGF-1 (12 to 15 hours)<\/li>\n
- After surgery (for acromegaly)<\/li>\n<\/ul>\n
Glucose suppression testing<\/h2>\n
The gold standard confirmatory test<\/strong> for acromegaly is the glucose suppression test. An inability to appropriately suppress serum growth hormone<\/strong> (GH) below 1ng\/ml after a 75g oral glucose load.<\/p>\n
These are causes of elevated (non-suppressible) GH after a glucose tolerance test<\/h4>\n
- \n
- Uncontrolled diabetes mellitus<\/li>\n
- Hypothyroidism<\/li>\n
- Pubertal growth spurt<\/li>\n
- Pregnancy<\/li>\n
- Depression<\/li>\n
- Chronic liver disease<\/li>\n
- Chronic kidney disease<\/li>\n
- Anorexia nervosa.<\/li>\n<\/ul>\n
Clinical Question<\/h2>\n
![\"Acromegaly](\"https:\/\/endoconsult.b-cdn.net\/wp-content\/uploads\/Acromegaly-IGF1-and-GH-discrepancy-Mind-Map-min.jpg\")
<\/a>Acromegaly IGF1 and GH discrepancy Mind Map<\/p>\nA patient with clinical features of acromegaly, elevated IGF-1, and a non-suppressed <\/a>growth hormone<\/a> (after an oral glucose load) has no demonstrable adenoma on pituitary imaging. What are the possible differential diagnoses?<\/p>\n
- \n
- Silent apoplexy<\/a> of a somatotroph tumor<\/li>\n
- An ectopic source of Growth hormone-releasing hormone (GHRH) neuroendocrine tumor<\/li>\n
- An ectopic source of Growth hormone (GH) neuroendocrine tumor<\/li>\n
- McCune-Albright syndrome<\/li>\n
- An ectopic pituitary<\/a> adenoma (sphenoid sinus)<\/li>\n<\/ul>\n
References<\/h2>\n
- Silent apoplexy<\/a> of a somatotroph tumor<\/li>\n