[Clinical reasoning and decision making in clinical practice: a boy with fatigue and abdominal pain].

A 14-year-old boy presented with fatigue and abdominal pain. Laboratory tests revealed a primary hypothyroidism with circulating auto-antibodies against thyroid peroxidase (TPO), anaemia and an elevated level of creatine kinase (CK). A diagnosis of auto-immune hypothyroidism with associated anaemia and myopathy was made. Thyroid hormone replacement therapy was started. However, six months later, he still complained of fatigue. He had unexpectedly varying thyroid function tests and the anaemia and the elevated level of CK persisted. Analysis of the other hormonal axes demonstrated a secondary adrenal insufficiency which was treated with hydrocortisone suppletion therapy. If a patient suffering from hypothyroidism does not respond appropriately to therapy or even deteriorates, adrenal insufficiency should always be considered. Patients with one type of auto-immune endocrinopathy have a greater risk at developing other types of auto-immune endocrinopathies.