Caloric restriction as a possible pitfall for persistent acromegaly follow-up – case report

BACKGROUND: Acromegaly diagnosis is established when plasma levels of IGF-1 are increased and the Oral Glucose Tolerance Test (OGTT) with 75gr of glucose can’t suppress Growth Hormone (GH) levels. These two parameters are also useful during follow-up, after surgical/radiologic therapy and/or during medical therapy. CASE PRESENTATION: A 29-year-old woman was diagnosed with acromegaly after a severe headache. Previous amenorrhea and facial and acral changes were noticed. A pituitary macroadenoma was found, biochemical evaluation was in agreement with the suspected acromegaly and a transsphenoidal adenectomy was performed. As the disease recurred, a surgical reintervention and radiosurgery (Gamma Knife, 22 Gy) were necessary. No normalization of IGF-1 was achieved during three years after radiosurgery. Surprisingly, then, and although clinical features seemed getting worse, IGF-1 levels became consistently controlled to 0.3–0.8 times the upper limit of the reference range. Questioned, the patient referred that she was following an intermittent fasting dietary plan. However, based on the dietary questionnaire, she was found to be under severe caloric restriction. First OGTT (under caloric restriction) showed absence of GH suppression and an IGF-1 value of 234 ng/dL (Reference Range 76–286 ng/mL). A second OGTT, one month after an eucaloric diet was instituted, showed an increased IGF-1 of 294 ng/dL, maintaining an unsuppressed, yet less elevated, GH. CONCLUSIONS: GHRH/GH/IGF-1 axis controls somatic growth. Regulation is complex, and nutrition status and feeding pattern have a recognized role. Like systemic inflammation or chronic liver disease, fasting and malnutrition decrease the expression of hepatic GH receptors, with consequent reduction of IGF-1 levels, through resistance to GH. This clinical report shows that caloric restriction may represent a pitfall in acromegaly follow-up.