Blood Tests for Diagnosing Hypopituitarism
A comprehensive panel of blood tests is essential for diagnosing hypopituitarism, including measurement of all anterior pituitary hormones and their target hormones, with some requiring dynamic stimulation tests for accurate diagnosis. 1
Initial Laboratory Evaluation
Morning (8 AM) baseline hormone measurements should include 2:
- Thyroid function: TSH and free T4
- Adrenal function: ACTH and cortisol
- Glycemic control: Glucose and HbA1c
- Gonadal function: Testosterone (men), estradiol (women), FSH, and LH
Routine prolactin testing is recommended in all patients with suspected pituitary dysfunction to rule out hypersecretion that might not be clinically suspected 2
Insulin-like growth factor 1 (IGF-1) evaluation is recommended to assess growth hormone status and rule out GH hypersecretion 2
Dynamic Stimulation Tests
For adrenal function: 1 mcg cosyntropin stimulation test is recommended when baseline morning cortisol levels are equivocal 2
For growth hormone deficiency: Dynamic stimulation tests are required as baseline GH levels are not diagnostic 1, 3
These tests should be performed prior to administration of steroids to avoid interference with results 2
Diagnostic Criteria for Hypophysitis
- Proposed confirmation criteria include 2:
- ≥1 pituitary hormone deficiency (TSH or ACTH deficiency required) combined with an MRI abnormality, OR
- ≥2 pituitary hormone deficiencies (TSH or ACTH deficiency required) in the presence of headache and other symptoms
Monitoring Schedule
Thyroid function (TSH and free T4) should be repeated before each treatment cycle 2
Early morning ACTH and cortisol levels should be monitored 2:
- Every month for 6 months
- Then every 3 months for 6 months
- Then every 6 months for 1 year
Interpretation of Results
Central hypothyroidism presents with low free T4 with low/normal TSH (unlike primary hypothyroidism where TSH is elevated) 2
Central adrenal insufficiency shows low cortisol with low/normal ACTH 2
Hypogonadotropic hypogonadism presents with low testosterone/estradiol with low/normal FSH and LH 2
The GH axis is most commonly affected in hypopituitarism (61-100% of patients), followed by gonadal axis (36-96%), adrenal axis (17-62%), and thyroid axis (8-81%) 1
Special Considerations
Patients with 3 or more pituitary hormone deficiencies are more likely to have GH deficiency and may not need dynamic testing 1
In cases of both adrenal insufficiency and hypothyroidism, steroids should always be started prior to thyroid hormone replacement to avoid precipitating an adrenal crisis 2
Diagnosis of hypopituitarism can be straightforward by measuring reduced basal hormone levels, but dynamic stimulation tests are frequently indicated for equivocal results or to diagnose partial hormone deficiencies 4, 3
MRI of the sella with pituitary cuts should be performed in patients with suspected hypophysitis or other structural causes of hypopituitarism 2
Diabetes insipidus is uncommon in nonfunctioning pituitary adenomas, reported in only 7% of patients at presentation 1