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CASE STUDY

CASE STUDY

A 7-year-old boy (height 113 cm, 5th percentile; weight 23 kg, approximately 50th percentile) presents with short stature. Review of growth chart demonstrates normal birth weight and birth length and growth velocity until a markedly decreased growth velocity over the past 2 years, and decrease from 50th height percentile. Review of history reveals headaches, increased urination, and orthostasis with febrile illnesses. Physical examination demonstrates short stature, mild generalized obesity, visual field defect, and normal prepubertal external male genitalia. The patient is diagnosed with a hypothalamic tumor. After completion of treatment protocol including resection and radiation, laboratory evaluations demonstrate growth hormone (GH) deficiency and a delayed bone age of 18 months. The patient is treated with recombinant human GH at a dose of 40 mcg/kg per day subcutaneously. After 1 year of treatment, his height velocity has increased from 5 cm/y to 11 cm/y. How does GH stimulate growth in children? What other hormone deficiencies are suggested by the patient’s history and physical examination? What other hormone replacements is this patient likely to require?

The control of metabolism, growth, and reproduction is mediated by a combination of neural and endocrine systems located in the hypothalamus and pituitary gland. The pituitary weighs about 0.6 g and rests at the base of the brain in the bony sella turcica near the optic chiasm and the cavernous sinuses. The pituitary consists of an anterior lobe (adenohypophysis) and a posterior lobe (neurohypophysis) (Figure 37–1). It is connected to the overlying hypothalamus by a stalk of neurosecretory fibers and blood vessels, including a portal venous system that drains the hypothalamus and perfuses the anterior pituitary. The portal venous system carries small regulatory hormones (Figure 37–1, Table 37–1) from the hypothalamus to the anterior pituitary.

FIGURE 37–1

The hypothalamic-pituitary endocrine system. Hormones released from the anterior pituitary stimulate the production of hormones by a peripheral endocrine gland, the liver, or other tissues, or act directly on target tissues. Prolactin and the hormones released from the posterior pituitary (vasopressin and oxytocin) act directly on target tissues. Hypothalamic factors regulate the release of anterior pituitary hormones. ACTH, adrenocorticotropin; ADH, antidiuretic hormone [vasopressin]; CRH, corticotropin-releasing hormone; DA, dopamine; FSH, follicle-stimulating hormone; GH, growth hormone; GHRH, growth hormone-releasing hormone; GnRH, gonadotropin-releasing hormone; LH, luteinizing hormone; PRL, prolactin; SST, somatostatin; TRH, thyrotropin-releasing hormone; TSH, thyroid-stimulating hormone.

TABLE 37–1Links between hypothalamic, anterior pituitary, and target organ hormone or mediator.1

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