ODP058 Topiramate causing elevation of urinary cortisol assay

Abstract

Abstract 69-year-old female with pituitary adenoma status-post transsphenoidal resection 6 years prior and isolated growth hormone deficiency [on somatropin 0.2 mg daily], migraines [on topiramate 25 mg daily], left lipid-rich adrenal incidentaloma, primary hypothyroidism [on levothyroxine 75 mcg daily], and secondary hyperparathyroidism from vitamin-D deficiency [on ergocalciferol 50000 IU weekly] and hydrochlorothiazide 25 mg daily presented for follow-up. Physical exam: afebrile, blood pressure hypertensive at 163/71 mmHg, heart rate 91 beats per minute, respiratory rate 18 breaths per minute, saturating 100% on room air and patient weighed 105 kg. Patient appeared obese but did not exhibit cervicodorsal fat pads, abdominal striae, or other cushingoid features. Neck was supple and did not demonstrate palpable nodules or lymphadenopathy. Labs ordered at clinic visit demonstrated normal TSH 1.28 with normal free T4 1.21, elevated PTH 232 with corrected calcium 9.7 (on hydrochlorothiazide) and normal vitamin-D, 25 level 43, normal ACTH 21, and normal IGF-1 level 75. Given adrenal incidentaloma and prior pituitary adenoma, the integrity of the hypothalamus-pituitary-adrenal axis was also tested. A subsequent 8: 00 a. m. cortisol was insufficiently suppressed at 5.2 after 1 mg dexamethasone suppression test which raised concern for hypercortisolism from pituitary adenoma or adrenal adenoma. Accordingly, ACTH as well as DHEA-S and 24 hour urine cortisol as well as midnight salivary cortisol level was ordered to assess pituitary versus adrenal origin, respectively. Interestingly, while midnight salivary cortisol was found to be normal at less than 50, the 24 hour urine cortisol measurement was elevated at 878 despite otherwise normal cortisol findings. ACTH and DHEA-S levels are still pending. Plan was made to check two additional midnight cortisol levels and await ACTH and DHEA-S levels. In an effort to explain the urinary cortisol elevation, the patient's medications were reviewed and subsequent literature search revealed that topiramate may interfere with urinary cortisol measurement by causing a dose-dependent increase in the measured urinary cortisol, presumably due to its action on the kidney during renal excretion. Patient had been on topiramate for approximately 6 months prior to this assay. Presentation: No date and time listed