1st order laboratory parameters – obligatory laboratory tests.
- Stage I
- Serum IGF-I (insulin-like growth factor-I; somatomedin) [serum IGF-I: ↑]
- Stage II
- Growth hormone suppression test after oral glucose loading (gold standard); blood samples for determination of growth hormone and glucose are taken at time points 0, 30, 60, 90, and 120 min – administration of glucose results in suppression of growth hormone secretion (serum GH) in healthy subjects[Adequate suppression of growth hormone to < 0.4 μg/dl excludes acromegaly].
- Somatotropic hormone (STH) (synonyms: somatotropin; English somatotropic hormone; HGH or hGH (human growth hormone), GH (growth hormone), growth hormone) – if acromegaly is suspected [serum GH ↑; GH concentration is usually basally elevated; however, since GH is secreted episodically, the significance of a single value is very limited]
- Prolactin (possibly also increased, wg, compression of the pituitary stalk).
- Thyroid parameters – TSH
- Gonadotropins – LH, FSH
- Sex steroids
- Glucose tolerance test (gold standard) – administration of glucose leads to suppression of growth hormone secretion (serum GH) in healthy individuals, i.e., if growth hormone levels < 1 μg/L are not achieved, the diagnosis of acromegaly is confirmed. Oral glucose tolerance test (oGTT with 75 g glucose) [with determination of GH]; blood samples for the determination of growth hormone and glucose are taken at the time points 0, 30, 60, 90 and 120 min – due toexclusion of reduced glucose tolerance [see above, GH is not suppressible by glucose in acromegaly!].
Therapy monitoring
- GH (hGH; STH) in oral glucose tolerance test (< 0.5 μg/L).