From the Guidelines
Laboratory tests to assess pituitary function include measurements of ACTH, cortisol, TSH, free T4, LH, FSH, testosterone, and estrogen, as well as dynamic testing such as ACTH stimulation and MRI imaging of the pituitary gland. According to the most recent evidence 1, the initial workup and evaluation of pituitary function should include:
- Baseline measurements of ACTH, cortisol, TSH, free T4, and electrolytes
- Consideration of standard-dose ACTH stimulation testing for indeterminate results
- Evaluation of LH and testosterone in males, FSH, and estrogen in premenopausal females with fatigue, loss of libido, and mood changes, or oligomenorrhea
- MRI brain with or without contrast with pituitary or sellar cuts in all patients with new hormonal deficiencies and particularly those with multiple endocrine abnormalities, severe headaches, or complaints of vision changes
The use of MRI imaging is supported by evidence 1, which suggests that MRI with high-resolution protocols is the best first-line test to evaluate the sella turcica and parasellar region. Additionally, dynamic testing such as ACTH stimulation 1 and water deprivation tests [example] may be necessary to assess posterior pituitary function and diagnose diabetes insipidus.
It is essential to interpret these tests in clinical context, often requiring multiple measurements and specialized endocrinology consultation 1. The most recent guideline 1 also emphasizes the importance of considering clinical features, such as excess height or acromegalic features, when diagnosing and managing pituitary adenomas in childhood and adolescence.
In terms of specific tests, the most recent evidence 1 recommends evaluating ACTH, cortisol, TSH, free T4, and electrolytes as the initial step in assessing pituitary function. This approach is supported by the evidence and is essential for diagnosing and managing pituitary disorders.
From the Research
Laboratory Tests for Pituitary Function
The following laboratory tests are used to assess pituitary function:
- Insulin tolerance test (ITT) 2, 3
- Low-dose adrenocorticotrophic hormone (ACTH) stimulation test 2, 3, 4
- Glucagon stimulation test (GST) 2
- Corticotropin releasing hormone (CRH) test 3
- Luteinizing hormone-releasing hormone (LH-RH) test 5, 6
- Thyrotropin releasing hormone (TRH) test 5, 6
Dynamic Stimulation Tests
Dynamic stimulation tests are used to evaluate the hypothalamo-pituitary-adrenal (HPA) axis and the growth hormone (GH)-insulin-like growth factor 1 (IGF-1) axis. These tests include:
- ITT: considered the gold-standard test for evaluating both HPA and GH-IGF-1 axes 2, 3
- Low-dose ACTH stimulation test: a sensitive, safe, and easily applicable alternative to ITT 2, 4
- GST: a good alternative to ITT, can evaluate both HPA and GH-IGF-1 axes 2
Other Tests
Other tests used to assess pituitary function include: