Persistent SIADH-like Hyponatremia Requiring Tolvaptan Despite Glucocorticoid Replacement in Rathke’s Cleft Cyst-Associated Hypophysitis: A Therapeutic Dilemma
Abstract
A 52-year-old man presented with severe hyponatremia and Rathke's cleft cyst (RCC)-associated hypophysitis with enlargement of the pituitary stalk. Hyponatremia persisted despite treatment with high-dose hydrocortisone, hypertonic saline, and loop diuretics, ultimately requiring low-dose tolvaptan. Hyponatremia associated with RCC is usually attributed to secondary adrenal insufficiency (SAI), in which glucocorticoid replacement generally restores free water excretion but may unmask arginine vasopressin deficiency (AVP-D). In the present case, however, persistent AVP-mediated water retention beyond SAI appeared to predominate, suggesting AVP dysregulation associated with inflammatory pituitary involvement. This case highlights the therapeutic dilemma of balancing masked AVP-D against persistent AVP excess in hyponatremia associated with RCC.
Related
- Glucocorticoid replacement therapy and anthropometric features in patients with 21-hydroxylase deficiency in Japan: results from a nationwide epidemiological study
- Continuous glucose monitoring reveals glycemic profile in adrenal insufficiency patients on glucocorticoid replacement
- Satellite cell glucocorticoid receptor restrains myogenic commitment without mediating the effects of therapeutic glucocorticoids on muscle repair
- Glucocorticoid receptor activation reorganizes Wnt/LEF1 regulatory circuitry associated with therapeutic response in B-cell acute lymphoblastic leukemia
- Fulminant Ischemic Colitis With Toxic Megacolon in a Young Man Receiving Testosterone Replacement Therapy Despite Therapeutic Phlebotomy for Hereditary Hemochromatosis: A Case Report
BibTeX
@article{shimizu2026persistent,
title = {{Persistent SIADH-like Hyponatremia Requiring Tolvaptan Despite Glucocorticoid Replacement in Rathke’s Cleft Cyst-Associated Hypophysitis: A Therapeutic Dilemma}},
author = {Yuya Shimizu and Reo Ishii and Kazumasa Tanaka and Koki Kinoshita and Jun Toyama and Noriaki Fukuhara and Masahiro Nezu},
journal = {Internal Medicine},
year = {2026},
month = oct,
doi = {10.2169/internalmedicine.7951-26},
url = {https://www.jstage.jst.go.jp/article/internalmedicine/advpub/0/advpub_7951-26/_article},
note = {CC BY-NC-ND},
}
RIS
TY - JOUR
TI - Persistent SIADH-like Hyponatremia Requiring Tolvaptan Despite Glucocorticoid Replacement in Rathke’s Cleft Cyst-Associated Hypophysitis: A Therapeutic Dilemma
AU - Yuya Shimizu
AU - Reo Ishii
AU - Kazumasa Tanaka
AU - Koki Kinoshita
AU - Jun Toyama
AU - Noriaki Fukuhara
AU - Masahiro Nezu
PY - 2026
DA - 2026/10/08
JO - Internal Medicine
DO - 10.2169/internalmedicine.7951-26
UR - https://www.jstage.jst.go.jp/article/internalmedicine/advpub/0/advpub_7951-26/_article
AB - A 52-year-old man presented with severe hyponatremia and Rathke's cleft cyst (RCC)-associated hypophysitis with enlargement of the pituitary stalk. Hyponatremia persisted despite treatment with high-dose hydrocortisone, hypertonic saline, and loop diuretics, ultimately requiring low-dose tolvaptan. Hyponatremia associated with RCC is usually attributed to secondary adrenal insufficiency (SAI), in which glucocorticoid replacement generally restores free water excretion but may unmask arginine vasopressin deficiency (AVP-D). In the present case, however, persistent AVP-mediated water retention beyond SAI appeared to predominate, suggesting AVP dysregulation associated with inflammatory pituitary involvement. This case highlights the therapeutic dilemma of balancing masked AVP-D against persistent AVP excess in hyponatremia associated with RCC.
SN - 1349-7235
SN - 0918-2918
ER -