Cushing’s Disease: Not Always Black and White

Abstract

\n Cushing’s Disease is a well known entity but the difficulty of diagnosis is often underappreciated. Given the wide spectrum of clinical presentation and pitfalls with each diagnostic evaluation, diagnosis of Cushing’s Disease (CD) is often difficult in clinical practice, even with pathological analysis. A 37 year old female with a history of Cushing’s Disease presented for her third transphenoidal resection to our institution. She was diagnosed with a pituitary microadenoma 16 years ago based on MRI, as she had persistent headaches and vision abnormalities. The patient also reported unexplained weight gain, “buffalo hump”, and moon facies at the time. She was diagnosed with CD due to an abnormal 1 mg overnight dexamethasone suppression test (DST) with AM cortisol of 3.03 ug/dl (normal <1.8 microgram/dl). She was on an oral contraceptive pill (OCP) at the time. The patient underwent her first pituitary transsphenoidal resection and was symptom free for about 10 years, after which she had a recurrence of her initial symptoms. She had another abnormal DST while on an OCP and pituitary MRI revealed growth of the pituitary adenoma. Patient underwent a second pituitary surgery with benign postoperative course with a recurrence about 5 years later. The workup prior to her third surgery revealed an abnormal DST while on OC pills with the 8am cortisol being 3.36 ug/dl (<1.8ug/dl), urinary free cortisol 35.4 mcg/24 hour (4-50 mcg/24 hour). 8am ACTH done on a separate day was 48 pg/ml (6-50 pg/ml) with a cortisol of 14.5 ug/dl. Midnight salivary cortisol was not performed. Interval history was still positive for weight gain and headaches, hence she was referred for her third pituitary surgery. Post surgery, the patient was on a short taper of hydrocortisone and 8am cortisol was 32 ug/dl the next day. After a discussion with the pathologist, it was determined that the pathology was suggestive of a corticotroph adenoma with moderate ACTH staining and patchy nuclear staining for TPIT, although the pathologist stated that it was difficult to be certain due to the small tissue size. From the current literature, this patient had an incomplete and equivocal biochemical work up while on OCPs but still had tissue diagnosis supporting CD. Whether this was a recurrence of Cushing’s disease, silent corticotroph adenoma, or non-functioning pituitary adenoma is unclear. This case illustrates the multiple challenges in the diagnosis of Cushing’s disease that may be encountered. 1.Braun LT et al. Recurrence after pituitary surgery in adult Cushing’s disease: a systematic review on diagnosis and treatment. Endocrine. 2020;70(2):218-231.