What blood work testing is relevant for suspecting Sheehan syndrome?

Blood Work Testing for Suspecting Sheehan's Syndrome

The most relevant blood work tests for suspecting Sheehan's syndrome include anterior pituitary hormone panel (TSH, free T4, cortisol, ACTH, FSH, LH, estradiol, prolactin, and GH/IGF-1), serum sodium, and complete metabolic panel. 1, 2

Initial Laboratory Evaluation

• Complete blood count with differential to assess for anemia or other hematologic abnormalities that may be present in hypopituitarism 2
• Comprehensive metabolic panel including electrolytes, liver function tests, and kidney function to identify metabolic derangements 3
• Serum sodium is particularly important as hyponatremia is present in approximately 35% of patients with Sheehan's syndrome 4, 3

Specific Hormone Testing

Essential Hormone Tests:

• Thyroid function tests: TSH and free T4 to identify secondary hypothyroidism (90% of patients have secondary hypothyroidism) 4
• Adrenal axis assessment: Morning cortisol and ACTH levels to evaluate for secondary adrenal insufficiency (55% of patients have adrenal failure) 4
• Gonadal axis: FSH, LH, and estradiol to confirm hypogonadotropic hypogonadism (present in nearly all patients) 2, 4
• Prolactin levels: Typically low in Sheehan's syndrome; baseline prolactin below 4.0 ng/ml is highly suggestive of prolactin deficiency 2
• Growth hormone axis: IGF-1 levels to screen for growth hormone deficiency (present in most patients) 4, 5

Dynamic Testing

• Combined pituitary stimulation test can be performed to assess the degree of hypopituitarism and confirm the diagnosis 1
• TRH stimulation test for prolactin response has high sensitivity and specificity for diagnosing prolactin deficiency in Sheehan's syndrome 2
• ACTH stimulation test (Synacthen/cosyntropin test) to evaluate adrenal reserve and confirm secondary adrenal insufficiency 4

Interpretation Considerations

• Lack of appropriate prolactin response to TRH stimulation is one of the most sensitive diagnostic signs 2, 4
• Secondary hypothyroidism in Sheehan's syndrome presents with low or normal TSH with low free T4 (unlike primary hypothyroidism where TSH is elevated) 4
• Secondary adrenal insufficiency presents with low cortisol and low or normal ACTH levels 4

Clinical Pearls and Pitfalls

• The diagnosis is often delayed by an average of 19.7 years, so a high index of suspicion is needed in women with history of postpartum hemorrhage 2
• Failure of lactation postpartum and amenorrhea are the most common presenting symptoms and should prompt hormonal evaluation 4, 5
• Hyponatremia may be the presenting feature and can be severe in some cases 3
• The number of deficient hormones tends to increase over time, so periodic reassessment is necessary even if initial testing shows only partial hypopituitarism 2

Imaging Considerations

While not a blood test, magnetic resonance imaging (MRI) of the pituitary should be performed to support the diagnosis:

• Empty or partially empty sella is a characteristic finding in all patients with classical Sheehan's syndrome 1, 4
• Mean sella volume is significantly lower in Sheehan's syndrome patients compared to healthy controls 2