Long-term Changes in Serum IGF-1 Levels After Successful Surgical Treatment of Growth Hormone–Secreting Pituitary Adenoma

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Abstract

BACKGROUND:

Successful treatment of acromegaly is known to normalize serum insulin-like growth factor 1 (IGF-1) levels within days after surgery. However, our clinical observations indicate that many cases of acromegaly show delayed normalization of serum IGF-1 levels after complete tumor resection.

OBJECTIVE:

To study long-term changes of the serum IGF-1 levels in acromegalic patients for whom surgical treatment was thought to be successful.

METHODS:

A retrospective observational study was performed with 46 acromegalic patients with no residual tumor on sellar magnetic resonance imaging, and a nadir growth hormone of less than 0.4 μg/L on a postoperative oral glucose tolerance test.

RESULTS:

In all patients, serum IGF-1 levels returned to the normal reference values for age and sex during the observational period (12-132 months). The mean duration from the time of surgery until IGF-1 normalization was 10 months (range, 3 days-57 months). Twenty-seven patients (59%) reached normal IGF-1 ranges within 3 months of surgery, whereas 19 patients (41%) experienced delayed (>3 months) IGF-1 normalization. Eleven patients (24%) recovered normal IGF-1 levels 12 to 57 months after surgery. The possibility of delayed IGF-1 cure was increased 8.8-fold with an immediate postoperative IGF-1 level increase of 100 μg/L.

CONCLUSION:

Satisfactory remission of acromegaly by IGF-1 criteria was delayed in a large proportion of acromegalic patients, especially those with high postoperative IGF-1 levels. Hence, additional treatment can be delayed in clinically stable acromegalic patients who show no evidence of residual tumors on postoperative magnetic resonance imaging and a normal growth hormone suppressive response to a glucose load.

ABBREVIATIONS:

GH, growth hormone

ABBREVIATIONS:

IGF-1, insulin-like growth factor 1

ABBREVIATIONS:

OGTT, oral glucose tolerance test

ABBREVIATIONS:

SDS, SD score

ABBREVIATIONS:

TSA, transsphenoidal adenectomy

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