Patient Demographics
16-year 7-month-old Caucasian female.
Clinical Presentation
Referred by a neurosurgeon for evaluation of her endocrine status. She had a pituitary lesion and polyuria and polydipsia suggestive of diabetes insipidus (DI).
Past History
She had a few months' history of increased thirst and urinary frequency. She experienced headaches twice a week, regular menstrual cycles, and no significant changes in her weight or energy level. Her urine was “like water.”
Evaluation
Height was at the 25th percentile and weight was at the 50th percentile. Specific gravity on urinalysis was 1.010. An MRI showed an enlarged pituitary gland, a lesion on the pineal gland (a cyst or mass), and a pituitary lesion that could be interpreted as a Rathke's cleft cyst or macroadenoma. Follow-up MRI was recommended. Pituitary testing included a prolactin of 29 ng/mL (normal [nl] <24), IGF-1 of 346 ng/mL (nl range), TSH of 15 μU/mL (nl <5.5), FT4 of 1.03 ng/dL (nl 0.89–1.76), elevated antiperoxidase antibodies, and normal LH and FSH levels. AM cortisol was 47 μg/dL (nl 7–20), ACTH of 19 pg/mL (nl 6–48), PM cortisol of 25 μg/dL (nl 4–11), urinary free cortisol level of 56 μg/24 hours (nl 2–38), and a cortisol of 4 μg/dL after suppression with dexamethasone. A corticosteroid binding globulin (CBG) was 6.2 mg/dL (nl 2.3–3.9).
Interventions
She started at a low dose of desmopressin after an overnight fast both as a diagnostic study and for clinical therapy. Repeat electrolytes were normal. The thyroid abnormality, unrelated to her pituitary issue, showed Hashimoto thyroiditis. She was started on 75 μg thyroid supplementation. Because the elevated cortisol level resulted from CBG excess, she did not require treatment.
Discussion/Recommendations
Differential diagnoses included hypopitiutarism because of the abnormal MRI and symptoms of DI. Elevated cortisol levels were unexpected because she lacked symptoms or physical characteristics of elevated cortisol levels. Approximately 75% of the cortisol in circulation is bound to CBG. The cortisol is thought to be biologically active only when it is not bound to CBG. Health care providers need to consider differential diagnoses and not narrow their focus on expected findings and make an inaccurate diagnosis. The patient/family must understand that CBG excess caused the elevated cortisol levels and does not require treatment.
Article info
Identification
Copyright
© 2012 Published by Elsevier Inc.
