The biochemical diagnosis of acromegaly: revising the role of measurement of IGF-I and GH after glucose load in 5 questions

ABSTRACT

Introduction

Acromegaly is a rare disorder characterized by the excessive secretion of growth hormone (GH), mostly caused by pituitary adenomas. While in full-blown cases the diagnosis is easy to establish, milder cases are more challenging. Additionally, establishing whether full cure after surgery is reached may be difficult.

Areas covered

In this article, we will review the challenges posed by the variability in measurements of GH and its main effector insulin-like growth factor I (IGF-I) due to both biological changes, co-morbidities, and assays variability.

Expert opinion

Interpretation of GH and IGF-I assays is important in establishing an early diagnosis of acromegaly, in avoiding misdiagnosis, and in establishing if cure is achieved by surgery. Physicians should be familiar with the variables that affect measurements of these 2 hormones, and with the performance of the assays available in their practice.

KEYWORDS:

• Acromegaly
• growth hormone
• IGF-I
• competitive assay
• sandwich assay
• binding proteins
• body mass index

Article highlights

• With use of monoclonal antibodies and calibration standards, GH and IGF-I assays have evolved over the years becoming more accurate

• Despite improvements, there is often poor reproducibility between different assays

• Knowledge of the accuracy of the assays is mandatory for clinicians ordering these tests

• While in severe cases the biochemical diagnosis of acromegaly is obvious, in milder cases there is need for a glucose suppression test

• The cut-off of GH nadir after glucose is debated, but probably lower than recommended by published guideline

• Body mass index, sex, use of oral estrogen and glucose status influence the post-glucose GH nadir

• Serum IGF-I may take long time to normalize after surgery, and post glucose suppression helps in establishing if surgical cure has been achieved.

Reviewer disclosures

Peer reviewers on this manuscript have no relevant financial or otherrelationships to disclose.

Declaration of interest

The authors have no relevant affiliations or financial involvement with anyorganization or entity with a financial interest in or financial conflict withthe subject matter or materials discussed in the manuscript. This includesemployment, consultancies, honoraria, stock ownership or options, experttestimony, grants or patents received or pending, or royalties.

Additional information

Funding

This paper was not funded.