Systemic illness Marta Bondanelli Æ Maria Chiara Zatelli Æ Maria Rosaria Ambrosio Æ Ettore C. degli Uberti Published online: 11 April 2008 Ó Springer Science+Business Media, LLC 2008 Abstract Systemic illnesses are associated with altera- tions in the hypothalamic–pituitary–peripheral hormone axes, which represent part of the adaptive response to stressful events and may be influenced by type and severity of illness and/or pharmacological therapy. The pituitary gland responds to an acute stressful event with two secretory patterns: adrenocorticotropin (ACTH), prolactin (PRL) and growth hormone (GH) levels increase, while luteinizing hormone (LH), follicle-stimulating hormone (FSH) and thyrotropin (TSH) levels may either decrease or remain unchanged, associated with a decreased activity of their target organ. In protracted critical illness, there is a uniformly reduced pulsatile secretion of ACTH, TSH, LH, PRL and GH, causing a reduction in serum levels of the respective target-hormones. These adaptations are initially protective; however, if inadequate or excessive they may be dangerous and may contribute to the high morbidity and mortality risk of these patients. There is no consensus regarding the type of approach, as well as the criteria to use to define pituitary axis function in critically ill patients. We here provide a critical approach to pituitary axis evaluation during systemic illness. Keywords Pituitary function Á Dynamic tests Á Critical illness Á System disease Introduction Systemic illnesses may be associated with changes in hypothalamic–pituitary function, representing part of the adaptive response to stressful events. Pituitary function may be profoundly influenced by type and severity of illness and/or pharmacological therapy employed in the treatment of patients [1–3]. Among systemic diseases, critical illness is any condi- tion requiring support for failing vital organ function, either mechanical aids (mechanical ventilation, hemodyalis of filtration, cardiac assistance devices) and/or with pharma- cological agents (such as inotropes vasopressor), without which death would ensue. Critical illness is characterized by multiple and complex metabolic, immunological, and endocrine changes, primarily involving hypothalamo– pituitary peripheral hormone axes [1]. Pituitary plays a central role in the regulation of meta- bolic and immunologic homeostasis and is an important regulator of a variety of adaptive responses that allow survival during critical states of any type. The stress response is mediated mainly by the sympathoadrenal sys- tem (SAS), which includes the sympathetic nervous system (SNS) and the adrenal medulla, and by the hypothalamic– pituitary–adrenal (HPA) axis [2, 4]. During stressful con- ditions, growth, reproductive and thyroid axes are inhibited at many levels. Glucocorticoids suppress growth hormone (GH) and thyroid-stimulating hormone (TSH) secretion and exert an inhibitory effect on the pituitary gonadotrophs and the gonads [1, 5, 6]. These adaptations are initially protective for the human body; however, if inadequate or excessive they may be dangerous, causing endocrine, metabolic, autoimmune, and psychiatric disorders. More- over, alterations within the hypothalamo–pituitary– peripheral hormone axes may contribute to the high M. Bondanelli Á M. C. Zatelli Á M. R. Ambrosio Á E. C. degli Uberti (&) Section of Endocrinology, Department of Biomedical Sciences and Advanced Therapies, University of Ferrara, Via Savonarola, 9, Ferrara 44100, Italy e-mail: ti8@unife.it 123 Pituitary (2008) 11:187–207 DOI 10.1007/s11102-008-0112-8