From the Guidelines
The laboratory workup for a pituitary adenoma should include a comprehensive panel of hormone tests, with a strong emphasis on serum IGF1 level and oral glucose load test to assess GH excess, as recommended by the 2024 consensus guideline for the diagnosis and management of pituitary adenomas in childhood and adolescence 1.
Key Tests
- Serum IGF1 level: elevated levels in relation to age-adjusted, sex-adjusted, and Tanner stage-matched normal range support a diagnosis of GH excess 1
- Oral glucose load test: failure to suppress GH levels below 1 μg/l after an oral glucose load suggests GH excess, although this test may be challenging to interpret in adolescents due to physiological variations in GH secretion 1
Additional Considerations
- Dynamic pituitary assessment to evaluate possible hypofunction and hyperfunction of other anterior pituitary hormones is crucial in patients with GH excess, as hypofunction can occur in up to 35% of patients with somatotrophinomas 1
- Biochemical screening for pituitary hormone excess should be offered to all children and adolescents with syndromic diseases such as Carney complex, McCune–Albright syndrome, and MEN1 or MEN1-like disease, as these conditions are associated with an increased risk of pituitary adenomas 1
Interpretation of Results
- IGF1 values should be interpreted with caution, as they can be influenced by factors such as hypothyroidism, malnutrition, and severe infection, and may be falsely normal or low in some cases 1
- GH and IGF1 levels should be monitored at baseline and during follow-up in patients with GH excess to assess the hormone-producing activity of the adenoma and guide treatment decisions 1
From the Research
Pituitary Adenoma Lab Work Up
- The diagnosis of pituitary adenomas involves evaluating complete pituitary function, as hypopituitarism is common 2
- Lab work up for pituitary adenomas may include measurement of hormone levels, such as prolactin, growth hormone, adrenocorticotropic hormone (ACTH), and thyroid-stimulating hormone (TSH) 3, 4
- For prolactinomas, initial lab work up may include measurement of prolactin levels, and for growth hormone-secreting tumors, measurement of insulin-like growth factor 1 (IGF-1) and growth hormone levels 3, 4
- However, normal IGF-1 levels do not exclude growth hormone excess, and formal evaluation of growth hormone status with oral glucose tolerance testing may be necessary 5
- For ACTH-secreting tumors, measurement of a late-night salivary cortisol level is the best screening test, and petrosal sinus sampling for ACTH may be necessary to distinguish a pituitary from an ectopic source 3
- Patients with macroadenomas may require evaluation for hypopituitarism, and patients with tumors compressing the optic chiasm should be referred to an ophthalmologist for formal visual field testing 4
Types of Pituitary Adenomas
- Prolactinomas account for 32% to 66% of adenomas and present with amenorrhea, loss of libido, galactorrhea, and infertility in women and loss of libido, erectile dysfunction, and infertility in men 3, 4
- Growth hormone-secreting tumors account for 8% to 16% of tumors and usually present with enlargement of the lips, tongue, nose, hands, and feet 3
- ACTH-secreting tumors account for 2% to 6% of adenomas and are associated with obesity, hypertension, diabetes, and other morbidity 3
- Clinically nonfunctioning adenomas account for 15% to 54% of adenomas and present with mass effects 3, 4
Treatment of Pituitary Adenomas
- First-line therapy for prolactinomas consists of dopamine agonists, such as bromocriptine or cabergoline 3, 4, 2
- Transsphenoidal pituitary surgery is first-line therapy for other pituitary adenomas requiring treatment 3, 4
- Medical therapy, such as somatostatin analogues, cabergoline, and pegvisomant, may be necessary for growth hormone-secreting tumors 3
- Treatment of ACTH-secreting tumors may include adenoma resection and medical therapies, such as ketoconazole, mifepristone, and pasireotide 3