Thursday, July 31, 2008

A Simple and Cost-Effective Approach to Assessment of Pituitary ACTH and GH Reserve – Combined Use of the Overnight Metyrapone Test and IGF-I Standard

http://jcem.endojournals.org/cgi/content/abstract/jc.2008-0154v1

A Simple and Cost-Effective Approach to Assessment of Pituitary ACTH and GH Reserve – Combined Use of the Overnight Metyrapone Test and IGF-I Standard Deviation Scores

Submitted on January 22, 2008
Accepted on July 22, 2008

A Simple and Cost-Effective Approach to Assessment of Pituitary ACTH and GH Reserve – Combined Use of the Overnight Metyrapone Test and IGF-I Standard Deviation Scores

James Gibney*, Marie-Louise Healy, Thomas P. Smith, and T. Joseph McKenna

Department of Endocrinology and Department of Medicine, St. Vincent's University Hospital Elm Park and The Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Ireland

* To whom correspondence should be addressed. E-mail: james.gibney@amnch.ie.

Context: The insulin tolerance test (ITT) is the gold standard for assessment of ACTH and growth hormone (GH) reserve in patients with suspected hypopituitarism. It is labour-intensive and costly.

Objective: To determine whether use of the overnight metyrapone test (OMT) and plasma IGF-I standard deviation scores (IGF-I-SDS) could provide a cost-effective alternative to the ITT.

Design: A retrospective chart review

Setting: A teaching hospital

Participants and intervention: Charts from 100 patients with organic pituitary disorders were reviewed. All underwent the OMT unless 9am plasma cortisol was <80>450 nmol/l when ACTH-deficiency or ACTH-sufficiency respectively was diagnosed. Patients were considered GH-deficient if the age-related IGF-I-SDS was <-3 or if they had 3 or more other pituitary hormone deficiencies (PHDs). Patients were considered GH-sufficient if age-related IGF-I-SDS was greater than the 95th centile established from patients with known GHD. Thirty-three underwent an ITT.

Main Outcome Measures: The proportion of patients in whom ACTH and GH reserve could be assessed using OMT/IGF-I-SDS. The concordance with results obtained from ITT.

Results: Fifty-five patients were ACTH-sufficient and 45 were ACTH-deficient. Twenty-one were GH-sufficient and 33 were GH- deficient based on IGF-I-SDS and other PHDs, while 46 could not be classified. There was near-uniform concordance between OMT/IGF-I-SDS and ITT. Initial investigation using OMT/IGF-I-SDS resulted in a significant cost saving. Conclusions: ACTH and GH reserve can be accurately and cost-effectively investigated using OMT/IGF-I-SDS in approximately 50% of patients with organic pituitary disorders.

Key words: Hypopituitarism • Overnight Metyrapone Test • IGF-I