Pituitary Function and Pathophysiology

Background The anterior and posterior lobes of the pituitary gland control processes vital for survival of the individual and the species. Although growth in infancy and childhood depend on nutrition, genetics, and environment, thyroid hormone and growth hormone (GH) are essential contributors to growth. Thyroid hormone is a master regulator of the metabolic rate and neurologic development in utero, in infancy, and in childhood. The stress response requires the participation of cortisol. Together, cortisol and GH help maintain normal plasma glucose levels. Although prolactin is also a stress hormone, its role in lactation is evolutionarily required for the nutrition, hydration, and survival of the newborn and infant. The survival of the species is dependent upon reproduction and the gonadotropins, which regulate spermatogenesis and ovulation beginning during puberty. The posterior pituitary is no less important than the anterior pituitary. Antidiuretic hormone (ADH) is a key regulator of water balance. Because humans are 60% water (and infants and children have proportionately more total body water than adults), maintenance of intracellular and extracellular volumes is necessary for health and survival. Lastly, oxytocin is involved in breast feeding and parturition. Collectively, the most complex endocrine systems involve the cerebral cortex, hypothalamus, anterior and posterior lobes of the pituitary, pituitary hormones, and target organs and tissues. Content This chapter focuses on disorders of the anterior and posterior pituitary that produce deficient or excess hormone activity. In some instances, more specific details are provided in other chapters that concern specific hormone systems. By necessity this chapter provides specific numerical values for reference intervals and diagnostic cut-offs. However, decision thresholds, physiologic ranges, and reference intervals provided in this chapter serve as a general guide. Laboratories should verify that these ranges are appropriate for use in their own settings because values may vary depending on methodologies and other factors.