Laboratory Evaluation for a 15-Year-Old Female with Hypopituitarism and Hypothyroidism Presenting with Fatigue
For a 15-year-old female with hypopituitarism and hypothyroidism on long-term prednisone who presents with fatigue and low energy, a comprehensive hormonal and metabolic evaluation should be ordered, focusing on pituitary function, thyroid status, and adrenal function.
Primary Laboratory Tests
- Morning ACTH and cortisol levels to assess adrenal function and determine if current prednisone dose is appropriate 1, 2
- TSH and Free T4 to evaluate thyroid function and adequacy of thyroid replacement 1, 2
- Free T3 to assess peripheral conversion of T4 to T3 2
- Complete blood count to rule out anemia 2
- Basic metabolic panel including electrolytes, glucose, BUN, and creatinine 2
- Liver function tests 2
Additional Hormone Evaluations
- FSH and estrogen levels - important in a female adolescent with hypopituitarism presenting with fatigue 1, 2
- IGF-1 (Insulin-like Growth Factor 1) to assess growth hormone status 2
- Fasting blood glucose and HbA1c to evaluate for diabetes or insulin resistance (particularly important in patients on long-term corticosteroids) 2
Specific Considerations for This Patient
Adrenal Function Assessment
- Standard-dose ACTH stimulation testing if morning cortisol results are indeterminate (between 3 μg/dL and 15 μg/dL) 1
- 24-hour urinary cortisol to assess overall cortisol status 2
Metabolic Evaluation
- Lipid profile - long-term prednisone use can affect lipid metabolism 2
- Serum ferritin, iron, TIBC, and transferrin saturation to rule out iron deficiency 2
- Vitamin B12 and folate levels to exclude deficiencies that may contribute to fatigue 2
- Vitamin D level - often deficient in patients with chronic illness 2
Interpretation Considerations
Laboratory results must be interpreted in the context of the patient's:
- Long-term prednisone use (10 mg for 20 years, which is unusual given her age of 15)
- Hypopituitarism diagnosis
- Hypothyroidism status and current treatment
Normal laboratory values don't necessarily rule out clinically significant hormone deficiencies 2
Important Pitfalls to Avoid
Don't focus solely on thyroid function - while hypothyroidism can cause fatigue, multiple hormone deficiencies may be present in hypopituitarism 1, 3
Don't overlook prednisone dose assessment - long-term prednisone use (especially at 10 mg daily) can disrupt glycometabolic homeostasis and contribute to fatigue 4
Don't miss hyponatremia evaluation - patients with hypopituitarism can develop hyponatremia, which may contribute to fatigue 5
Remember that TSH may not be reliable in central hypothyroidism - focus on Free T4 levels with a goal in the upper half of the reference range 1
Consider DHEA testing in females with low energy who are otherwise adequately replaced with hormones 1
By systematically evaluating these laboratory parameters, you can identify the underlying cause of fatigue in this patient with complex endocrine disorders and optimize her hormone replacement therapy.