From the Guidelines
This 52-year-old female with a pituitary adenoma, fatigue, headaches, IGF-1 of 93, and IGF-1 z-score of -0.8 is not considered growth hormone deficient based on current guidelines. The diagnosis of growth hormone deficiency (GHD) typically requires a combination of low IGF-1 levels, often with a z-score below -2.0, and confirmatory stimulation testing 1. In this case, the patient's IGF-1 z-score of -0.8 falls within the normal range, suggesting normal growth hormone function despite the presence of a pituitary adenoma.
Key Considerations
- The patient's fatigue and headaches are likely related to the adenoma itself rather than growth hormone deficiency.
- Management should focus on addressing the pituitary adenoma through neurosurgical consultation, regular MRI monitoring, and treating specific hormonal abnormalities if present.
- According to the consensus on diagnosis and management of Cushing's disease, serum IGF-I level alone is not likely to be a reliable indicator of GHD, as levels can be in the lower half of the normal range on dynamic tests 1.
- Patients with macroadenomas and more aggressive surgical resection are at higher risk for hypopituitarism; however, this patient's current IGF-1 levels do not indicate GHD.
Monitoring and Potential Testing
- If there is concern about possible growth hormone deficiency despite the normal IGF-1, dynamic testing such as insulin tolerance test or glucagon stimulation test could be considered, but is not indicated based on current values.
- The patient should be monitored for development of other pituitary hormone deficiencies, as pituitary adenomas can affect multiple hormonal axes over time.
- It is recommended to wait at least 6–12 months after surgery before considering GHD assessment, especially as postoperative HPA axis recovery is often delayed 1.
Treatment Approach
- The current approach should prioritize managing the pituitary adenoma and monitoring for any changes in hormonal status, rather than initiating growth hormone replacement therapy.
- Accessibility of GH replacement may be an important factor in determining testing and treatment considerations, but given the patient's current status, this is not immediately relevant 1.
From the Research
Diagnosis of Growth Hormone Deficiency
- The diagnosis of adult growth hormone deficiency (GHD) is based on biochemical tests and clinical context, as stated in the GH Research Society Consensus from Port Stevens in 1997 2.
- The insulin tolerance test (ITT) is considered the gold standard for diagnosing adult GHD, with a GH peak lower than 3 microg/L indicating severe GHD 2.
- Alternative provocative tests, such as arginine and glucagon, can be used if ITT is contraindicated, with appropriate cut-off limits 2.
- Serum insulin-like growth factor I (IGF-I) levels can be used as a screening tool, but lack sufficient sensitivity and specificity for diagnosing GHD in adults 3.
Clinical Context and Risk Factors
- Patients with hypothalamic or pituitary disease, history of cranial irradiation, or childhood-onset GHD are at risk for adult GHD 2, 3.
- Brain injuries, such as trauma or subarachnoid hemorrhage, can also cause acquired hypopituitarism, including GHD 2.
- Patients with multiple pituitary hormone deficiencies, risk factors for hypopituitarism, and low serum IGF-I levels are likely to be GH deficient 3.
Growth Hormone Replacement Therapy
- Recombinant human growth hormone (rhGH) replacement therapy is widely accepted for patients with GHD induced by pituitary adenoma, but its safety, particularly in patients with residual tumor, is a concern 4.
- Studies have shown that rhGH therapy does not increase the risk of pituitary tumor recurrence in patients with adult GHD caused by nonfunctioning pituitary adenoma or craniopharyngioma 5.
- GH replacement therapy has been shown to improve outcomes in adult patients with hypopituitarism, including reduced morbidity, improved exercise capacity, and enhanced quality of life 6.