Category: Pituitary Disorders/Neuroendocrinology
Defining the underlying etiology of abnormal sodium can be challenging. We present this case to increase awareness of secondary hypothyroidism and/or adrenal insufficiency secondary to pituitary mass as a cause of SIADH in patients with persistent hyponatremia.
An 81-year-old female presented with recurrent symptomatic hyponatremia since March 2018 with multiple ER visits and hospital admissions. She presented with generalized weakness and nausea and was found to have hyponatremia with sodium 124 meq/L (135 - 145).
She was initially diagnosed with SIADH and started on 1 gram of salt tablets twice daily in addition to 1.2 liters of fluid restriction daily. She was admitted again in November 2018 for hyponatremia and found to have low cortisol level 1 mcg/dL (4.3 - 19.8).
At this time, endocrinology was consulted for adrenal insufficiency. A cosyntropin test was performed with a peak cortisol level of 8.4 ug/dL and baseline ACTH < 5 pg/mL which is consistent with secondary adrenal insufficiency. On review, TSH was normal with no prior assessment of free T4.
Repeat thyroid function test again showed TSH within normal limit, but Free T4 was found to be low at 0.4 ng/dL (0.61 - 1.37).
This raised a concern for panhypopituitarism. FSH, LH, estradiol, prolactin, and alpha-subunit levels were consistent with panhypopituitarism. Pituitary MRI showed a 1.5x1x1.2 cm cystic sellar and suprasellar mass abutting the optic chiasm, likely representing a Rathke cleft cyst. She was started on Hydrocortisone and Levothyroxine resulting in normalization of her sodium level. Outpatient follow up with neurosurgery was planned.
Anchoring diagnosis of hyponatremia on SIADH is a common tendency before consideration of the full spectrum of differential diagnosis, leading to misdiagnosis. In this case, treatment was initiated with salt tablets and fluid restriction with no significant improvement.
This delay in the diagnosis of pituitary mass and panhypopituitarism could have been prevented if full appropriate thyroid and adrenal assessment had been performed earlier.
Conclusion : In a patient with euvolemic hyponatremia, it is essential to evaluate thyroid and adrenal axis with TSH, free T4, cortisol, and ACTH to rule out both primary and central disease processes. Normal TSH alone cannot rule out hypothyroidism in central disease.
Ghaydaa Adawi– Endocrinology Fellow, MSU Endocrinology, Holt, Michigan
Tariq Alrasheed– Endocrinology Fellow, MSU Endocrinology fellowship program
Atinuke Aluko– Resident, MSU internal medicine, Michigan
Naveen Kakumanu– Assistant Professor of Medicine, MSU Endocrinology
George M Hebdon– Endocrinology Fellowship Director, MSU Endocrinology
Endocrinology fellow at MSU Endocrinology
MSU Endocrinology fellowship program
Currently endocrinology fellow at MSU endocrinology
Assistant Professor of Medicine
Dr. Kakumanu joined the Department of Medicine at MSU on October, 2013. He graduated from Saint George’s University, School of Medicine in Grenada. He completed his residency in Internal Medicine at the Detroit Medical Center, Wayne State University and was Chief Medical Resident, ambulatory clinic preceptor at Harper/Hutzel University Hospital, Detroit Medical Center. He completed a Geriatric Fellowship at Wayne State University and received the Lavoisier Cardozo Award for Excellence in Geriatric Medicine. Endocrinology fellowship was completed at Henry Ford Hospital in 2013. He is board certified in Internal Medicine, Geriatric Medicine and Endocrinology. Has presented multiple posters and abstracts at the Endocrine Society, American Association of Clinical Endocrinologists and American Society for Bone and Mineral Research. His specialty in Endocrinology is diverse with interest in thyroid disorders, diabetes and bone metabolism.
Endocrinology Fellowship Director
G. Matthew Hebdon M.D., Ph.D. received his Ph.D. from the National Institute for Medical Research in London U.K. for work on the transport of Ca++ through lipid bilayers and the synthesis of lipid-selective photo-activated probes. Following post-Doctoral Research he was appointed Director of Chemotherapy for Glaxo Pharmaceuticals.
Dr. Hebdon received his M.D. from the University of North Carolina at Chapel Hill and completed Residencies in Internal Medicine and Pediatrics and Fellowships in Adult and Pediatric Endocrinology Nutrition and Metabolism at the University of Michigan. Before coming to Michigan State University he was at the University of Maryland. He is the Program Director for the Endocrinology and Metabolism Fellowship at M.S.U.