The Value of Circulating IGF-I Bioactivity in Untreated Acromegaly

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: SUN 130-162-Neuroendocrinology
Clinical
Sunday, June 16, 2013: 1:45 PM-3:45 PM
Expo Halls ABC (Moscone Center)

Poster Board SUN-153
Aimee J Varewijck*, Sebastian JCMM Neggers, Steven W Lamberts, Leo J Hofland and Joseph A M J L Janssen
Erasmus MC, Rotterdam, Netherlands
Context: The value of IGF-I bioactivity in untreated acromegaly is yet unknown.

Methods:An investigator-initiated cross-sectional study in fifteen new patients with active acromegaly based on clinical presentation, unsuppressed GH levels during an OGTT and elevated age-matched total IGF-I levels. IGF-I bioactivity was measured by the insulin-like growth factor-I receptor (IGF-IR) KIRA assay. Total IGF-I and IGFBP-3 were measured by immunoassay. Quality of life (QoL) was assessed by AcroQoL, PASQ and SF-36 questionnaire (SF-36Q).

Results:All subjects had total IGF-I levels above the normal range, while IGF-I bioactivity and IGFBP-3 were within the normal range in 67% and 47% of patients, respectively. Nevertheless, IGF-I bioactivity was positively related to random GH measurements, while such relationship was absent for total IGF-I.

Both total IGF-I and IGF-I bioactivity were significantly related to the PASQ (r=0.65, p=0.02 vs. r=0.57, p=0.05). Also, both total IGF-I and IGF-I bioactivity were inversely related to the physical component summary of the SF-36Q (r=-0.60, p=0.03 vs. -0.78, p=0.002). Moreover, IGF-I bioactivity, but not total IGF-I, was significantly inversely related to the physical dimension of the AcroQoL -0.58, p=0.04 vs. -0.35, p=0.24).

Conclusions Despite the fact acromegalic patients had total IGF-I levels above the upper limit of normal, a considerable number of patients had IGF-I bioactivity within the normal range. Nevertheless, IGF-I bioactivity was more strongly related to measures of QoL than total IGF-I suggesting that IGF-I bioactivity may better reflect physical limitations perceived by untreated acromegalic patients.

Nothing to Disclose: AJV, SJN, SWL, LJH, JAMJLJ

*Please take note of The Endocrine Society's News Embargo Policy at http://www.endo-society.org/endo2013/media.cfm

Sources of Research Support: This work was supported by an unrestricted grant from Novo Nordisk A/S (Alphen aan de Rijn, the Netherlands). Novo Nordisk A/S had no involvement in the study design, in the collection, analysis, and interpretation of data.