Which hormone tests should be performed for a comprehensive endocrine evaluation?

Comprehensive Endocrine Hormone Testing

For a comprehensive endocrine evaluation, perform baseline testing of all pituitary axes including morning cortisol with ACTH, free T4 with TSH, sex hormones (testosterone in men, estradiol/FSH/LH in women), prolactin, and IGF-1, with additional dynamic testing based on initial results and clinical context. 1, 2

Core Baseline Hormone Panel

The foundation of endocrine evaluation requires simultaneous assessment of multiple hormone axes:

Adrenal Axis

• Morning (8-9 AM) serum cortisol as the first-line test 1
• ACTH level (drawn simultaneously with cortisol) 1, 3
• Cortisol <3 µg/dL indicates adrenal insufficiency; >15 µg/dL likely excludes it 1
• For values between 3-15 µg/dL, proceed to ACTH stimulation test (peak cortisol <18.1 µg/dL at 30-60 minutes confirms insufficiency) 1
• Critical timing: Test at least 18-24 hours after last hydrocortisone dose, longer for synthetic glucocorticoids 1

Thyroid Axis

• Free T4 and TSH measured together 1, 2
• Low or low-normal free T4 with inappropriately normal/low TSH indicates central hypothyroidism 1
• In pituitary disease with low-normal free T4 and symptoms, consider starting levothyroxine or monitor for 20% decrease over time 1

Gonadal Axis

In men:

• Testosterone, FSH, and LH (before 10 AM, after overnight fast) 1
• Prolactin simultaneously to exclude hyperprolactinemia as cause of hypogonadism 1

In premenopausal women:

• If oligomenorrhea/amenorrhea present: estradiol, FSH, LH 1
• Exclude pregnancy first in amenorrhea cases 1
• Women with regular menses do not require gonadal hormone testing 2

In postmenopausal women:

• Absence of elevated FSH/LH confirms gonadotrope dysfunction (if not on hormone therapy) 1

Growth Hormone Axis

• IGF-1 level for screening 2
• Dynamic GH stimulation testing may be needed after correcting other hormone deficiencies 1

Prolactin

• Serum prolactin in all patients with pituitary lesions 2
• Screens for prolactinomas (6-18% of incidentalomas) and hyperprolactinemia affecting other axes 2

Screening for Hormone Hypersecretion

When evaluating pituitary masses or suspected hypersecretion:

Cushing's Syndrome Screening

Use one high-accuracy initial test 4:

• 24-hour urinary free cortisol, OR
• Late-night salivary cortisol, OR
• 1 mg overnight dexamethasone suppression test, OR
• 2 mg 48-hour dexamethasone suppression test

If abnormal: Refer to endocrinologist and perform second confirmatory test 4. Two concordant abnormal results warrant evaluation for Cushing's cause 4.

Important caveat: Avoid dexamethasone testing in pregnancy (use urinary free cortisol instead) and in patients on antiepileptic drugs that enhance dexamethasone clearance 4

Acromegaly Screening

• IGF-1 level in all patients with incidental pituitary adenomas 2
• Despite being "incidental," 17% of surgically-treated acromegaly cases were initially discovered incidentally, and 58% had retrospective clinical features 2

Context-Specific Testing Algorithms

For Primary Adrenal Insufficiency Workup

Adults 5:

1. Anti-21-hydroxylase antibodies as first-line (strong recommendation)
2. If negative: Adrenal CT to evaluate for structural causes (tuberculosis, hemorrhage, tumor)
3. If autoimmune and normal CT: Very long-chain fatty acids (especially in adolescent/adult males for adrenoleukodystrophy)
4. Discontinue anti-adrenal antibody testing (outdated, non-specific)

Children/adolescents with glucocorticoid ± mineralocorticoid deficiency 5:

1. Anti-21-hydroxylase antibodies first-line
2. If negative in males: Very long-chain fatty acids for adrenoleukodystrophy
3. If all negative: Consider DAX-1 gene testing, then gene panel sequencing

Newborns/infants 5:

1. Adrenal steroid assays via LC-MS/MS to detect congenital adrenal hyperplasia
2. If no enzyme deficiency: High-speed gene panel sequencing for rare causes

For Secondary (Central) Adrenal Insufficiency

If isolated ACTH deficiency 5:

• First suspect exogenous corticosteroid exposure (systemic or local administration)
• If no steroid history: Perform complete pituitary hormone evaluation and pituitary MRI 5

In newborns with ACTH deficiency 5:

• Complete pituitary examination
• Screen for cerebral, ocular, and cardiac malformations
• Consider genetic testing if multiple pituitary deficiencies present

For Pituitary Incidentalomas

All patients require 2, 6:

• Complete hormone testing regardless of lesion size or symptoms (presence/absence of symptoms doesn't correlate with dysfunction)
• Screening for both hypersecretion and hypopituitarism

Hypopituitarism risk 6:

• Microincidentalomas: Lower risk but can occur
• Macroincidentalomas: Higher risk (up to 30% gonadotropin deficiency, 18% ACTH deficiency, 28% TSH deficiency)
• Larger microincidentalomas (6-9 mm) may behave like macroadenomas

Follow-up timing 2:

• Repeat pituitary hormone evaluation at 1-2 years for all micro- and macroadenomas
• Earlier if new symptoms develop
• Repeat with any lesion enlargement

Critical Pitfalls to Avoid

1. Never use random cortisol levels for diagnosing adrenal insufficiency 1
2. Don't perform dynamic TSH or GnRH testing - they provide no useful diagnostic information 1
3. Always start glucocorticoid replacement before thyroid hormone in combined deficiencies to prevent adrenal crisis 3
4. Distinguish primary from secondary adrenal insufficiency by ACTH-cortisol relationship: low ACTH with low cortisol = central (secondary) insufficiency 3
5. In pregnancy: Use urinary free cortisol, not dexamethasone suppression tests 4
6. Test timing matters: Morning samples for cortisol/testosterone, appropriate washout periods for patients on glucocorticoids 1
7. Don't screen broadly for Cushing's without clinical features - high false-positive rate 2

When Dynamic Testing Is Required

• ACTH stimulation test: When morning cortisol 3-15 µg/dL 1
• GH stimulation testing: After correcting other pituitary deficiencies, in select patients 1
• Confirmatory Cushing's testing: Second test after abnormal screening test 4
• Water deprivation test: For suspected diabetes insipidus (polyuria >50 mL/kg/day with high serum osmolarity >295 mOsm/L but low urine osmolality) 1