We report a 14 year-old peripubertal girl who presented at our clinic with the primary complaint of delayed puberty. She was asymptomatic except for vague complaints of fatigue. Physical examination was significant for mucosal hyperpigmentation and lack of secondary sexual characteristics. Laboratory evaluation revealed a morning cortisol concentration of <0.1 microg/dl (normal range [n.r.]: 4.3-22.4 microg/dl) and a simultaneous ACTH concentration of 2 pg/ml (n.r. 25-62 pg/ml); FSH 66.8 IU/l (n.r. for age: 1-12.8 IU/l); LH 41.1 IU/l (n.r. for age: 1-12 IU/l); E2 38 pg/ml (n.r. for age: 7-60 pg/ml). She had a flat cortisol response to an ACTH stimulation test. MRI of the pituitary gland failed to reveal a lesion. Plasma renin activity, thyroid function tests, parathyroid hormone, prolactin, IGF-I, IGFBP-3 concentrations and serum electrolytes were normal. However, her urinary sodium concentration was high. She was diagnosed with autoimmune polyglandular endocrinopathy including ovarian failure, adrenal failure and autoimmune anterior hypophysitis presenting as isolated ACTH deficiency. We emphasize that autoimmune etiology should be considered in the differential diagnosis of delayed puberty and ovarian failure and that the presence of other endocrinopathies should be searched for even in asymptomatic patients.