Endocrine Abstracts

Introduction: Hypothalamic–pituitary sarcoidosis is uncommon and affects <10% of patients with neurosarcoidosis. It presents a diagnostic challenge. We present a case of isolated central hypoadrenalism presenting as the sole manifestation of neurosarcoidosis.

Case history: A 76-year-old man with recently diagnosed primary hypothyroidism presented with weight loss, increasing lethargy and fatigue. Physical exam revealed inguinal lymhadenopathy. Staging CT thorax showed bilateral mediastinal lymphadenopathy, interstitial lung parenchymal changes, and splenomegaly. Mild hypercalcaemia (calcium 2.65 mmol/l) and hyponatremia were noted.Initial differential diagnoses included lymphoma, malignancy, or granulomatous disease. Diagnostic excision biopsies of left inguinal and mediastinal lymph nodes were inconclusive. An empirical trial of steroid therapy for presumed sarcoidosis was commenced with symptomatic improvement in general well being. Withdrawal of steroids was attempted in view of the inclusive lymph node biopsies. This resulted in a marked deterioration in the patient with hypotension, listlessness and obtundation. Adrenal insufficiency was suspected. ACTH stimulation with tetracosactide (Synacthen) showed a sub-optimal cortisol increment with peak cortisol of 224 nmol/l. Adrenal antibodies were negative and serum ACTH level <5 mg/l suggesting secondary adrenal insufficiency This was confirmed by a subsequent long ACTH stimulation test. CT imaging showed no gross pituitary abnormality. The patient improved symptomatically on glucocorticoid replacement therapy.

Discussion: The exact mechanism of injury in hypothalamic–pituitary sarcoidosis is unclear. Endocrine dysfunction was attributed to granulomatous infiltration of the hypothalamus and pituitary though hypothalamic insufficiency and pituitary responsiveness to hypothalamic releasing factors are now thought to be the main cause of hypopituitarism. Central hypoadrenalism can present with protracted and non-specific symptoms and pose a diagnostic challenge in the absence of any gross structural pituitary abnormality. A high index of suspicion remains the cornerstone of diagnosis.