Biochemical criteria
Biochemical criteria for diagnosis of acromegaly is based on elevated age- and sex-matched plasma insulin-like growth factor 1 (IGF-1) in serum and absence of growth hormone suppression after an oral glucose load.[4]Fleseriu M, Langlois F, Lim DST, et al. Acromegaly: pathogenesis, diagnosis, and management. Lancet Diabetes Endocrinol. 2022 Nov;10(11):804-26.
http://www.ncbi.nlm.nih.gov/pubmed/36209758?tool=bestpractice.com
The cutoff of the GH nadir is <0.4 to 1 micrograms/L (depending on the assay used).[4]Fleseriu M, Langlois F, Lim DST, et al. Acromegaly: pathogenesis, diagnosis, and management. Lancet Diabetes Endocrinol. 2022 Nov;10(11):804-26.
http://www.ncbi.nlm.nih.gov/pubmed/36209758?tool=bestpractice.com
IGF-1 and GH levels are well correlated at GH levels <20 micrograms/L, but IGF-1 levels plateau when serum GH increases above that level.[21]D'Arcy R, Courtney CH, Graham U, et al. Twenty-four-hour growth hormone profiling in the assessment of acromegaly. Endocrinol Diabetes Metab. 2017 Dec 27;1(1):e00007.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6360915
http://www.ncbi.nlm.nih.gov/pubmed/30815544?tool=bestpractice.com
Imaging
Invasiveness of the pituitary adenoma is judged according to:[22]Serioli S, Doglietto F, Fiorindi A, et al. Pituitary adenomas and invasiveness from anatomo-surgical, radiological, and histological perspectives: a systematic literature review. Cancers (Basel). 2019 Dec 4;11(12):1936.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6966643
http://www.ncbi.nlm.nih.gov/pubmed/31817110?tool=bestpractice.com
Pituitary tumor volume
Suprasellar extension and compression of neural structures
Invasion of sphenoid bone and cavernous sinuses (Knosp grading 1 to 4).[23]Knosp E, Steiner E, Kitz K, et al. Pituitary adenomas with invasion of the cavernous sinus space: a magnetic resonance imaging classification compared with surgical findings. Neurosurgery. 1993 Oct;33(4):610-7; discussion 617-8.
http://www.ncbi.nlm.nih.gov/pubmed/8232800?tool=bestpractice.com