From the Guidelines
The most effective approach to assessing pituitary gland function involves a combination of blood tests to measure hormone levels, including ACTH, cortisol, TSH, free T4, and electrolytes, as well as imaging tests like MRI brain with pituitary or sellar cuts, especially in patients with new hormonal deficiencies or symptoms like severe headaches and vision changes. When evaluating pituitary gland function, it is crucial to consider the clinical context and symptoms presented by the patient. For instance, patients with fatigue, loss of libido, mood changes, or oligomenorrhea may require additional evaluations of LH, testosterone in males, FSH, and estrogen in premenopausal females 1. The initial workup should include:
- Evaluating ACTH (AM), cortisol (AM), TSH, free T4, and electrolytes
- Considering standard-dose ACTH stimulation testing for indeterminate results (AM cortisol < 3 mg/dL and < 15 mg/dL)
- Considering MRI brain with or without contrast with pituitary or sellar cuts in all patients with new hormonal deficiencies, particularly those with multiple endocrine abnormalities, new severe headaches, or complaints of vision changes 1. Furthermore, specific conditions may necessitate additional tests, such as diabetes insipidus, which warrants an MRI brain with or without contrast with pituitary or sellar cuts due to its common association with metastatic disease 1. By prioritizing these tests and considering the patient's clinical presentation, healthcare providers can effectively assess pituitary gland function and identify potential issues that may impact morbidity, mortality, and quality of life.
From the Research
Pituitary Gland Function Tests
To assess pituitary gland function, several tests can be employed, including:
- Stimulation tests with GnRH-TRH or arginine-GnRH-TRH to evaluate the serum levels of LH, FSH, PRL, HGH, TSH, and total thyroxine (T4) 2
- Insulin-induced hypoglycemia to assess the response of plasma GH 3
- Luteinizing hormone-releasing hormone (LH-RH) and thyrotropin-releasing hormone (TRH) tests to examine the responses of plasma LH, FSH, TSH, and prolactin 3
- Arginine infusion to measure GH values 4
- TRH test to evaluate the response of plasma TSH and prolactin 4
- LRH test to assess the gonadotrophin responses 4
Hormone-Specific Tests
Specific tests for various hormones can also be used, such as:
- Radioimmunoassay (RIA) to determine the serum levels of LH, FSH, PRL, HGH, TSH, and total thyroxine (T4) 2
- Double antibody radioimmunoassay to measure the alpha subunit of glycoprotein hormones 5
- Non-isotopic in situ hybridization method to examine GH, PRL, and human beta-chorionic gonadotropin (beta-hCG) gene expression in pituitary tumors 6
Patient-Specific Tests
The choice of test may depend on the patient's specific condition, such as:
- Cushing's syndrome: responses of plasma ACTH, GH, LH, FSH, TSH, and prolactin to hydrocortisone, lysine-8 vasopressin (LVP), insulin-induced hypoglycemia, LH-RH, and TRH 3
- Idiopathic haemochromatosis: measurements of basal plasma values of testosterone, LH, and FSH, and responses to LRH and TRH tests 4
- Pituitary adenomas: detection of GH, PRL, and beta-hCG mRNA by in situ hybridization using a non-isotopic detection method 6