Abstract
BACKGROUND: Small cell lung cancer (SCLC) accounts for 15% of lung cancers, and it commonly expresses peptide and protein factors that are active as hormones. These secreting factors manifest as paraneoplastic disorders, such as ectopic adrenocorticotropic hormone (ACTH) syndrome (EAS). The clinical features are abnormalities in carbohydrate metabolism, hypokalemia, peripheral edema, proximal myopathy, hypertension, hyperpigmentation, and severe systemic infection. However, it is uncommon that EAS has an influence on hypothalamus-pituitary function. CASE SUMMARY: A 62-year-old man presented with complaints of haemoptysis, polyuria, polydipsia, increased appetite, weight loss, and pigmentation. Following a series of laboratory and imaging examinations, he was diagnosed with SCLC, EAS, hypogonadism, hypothyroidism, and central diabetes insipidus. After three rounds of chemotherapy, levels of ACTH, cortisol, thyroid hormone, gonadal hormone, and urine volume had returned to normal levels. In addition, the pulmonary tumor was reduced in size. CONCLUSION: We report a rare case of SCLC complicated with panhypopituitarism due to EAS. We hypothesize that EAS induced high levels of serum glucocorticoid and negative feedback for the synthesis and secretion of antidiuretic hormone from the paraventricular nucleus, and trophic hormones from the anterior pituitary. Therefore, patients who present with symptoms of hypopituitarism, or even panhypopituitarism, with SCLC should be evaluated for EAS.