ADH, Antidiuretic hormone; CNS, central nervous system; E2, estradiol; FSH, follicle-stimulating hormone; GH, growth hormone; GnRH, gonadotropin-releasing hormone; IGF-1, insulin-like growth factor; IGFBP3, insulin-like growth factor-binding protein 3; LH, luteinizing hormone; MRI, magnetic resonance imaging; TRH, thyrotropin-releasing hormone; TSH, thyroid-stimulating hormone; T4, thyroxine.
*Each patient with hypopituitarism should have CNS MRI as part of evaluation to determine the etiology of the condition.
from this area or terminate in the mediobasal hypothalamus, DISORDERS OF THE from which they can exert effects on water balance, even in the HYPOTHALAMIC-PITUITARY AXIS absence of the posterior pituitary gland.
The assessment of pituitary function may be determined
Decision-Making Algorithms by measuring some of the specific pituitary hormone in the Available @ StudentConsult.com basal state; other assessments require the measurement after stimulation. Indirect assessment of pituitary function can be obtained by measuring serum concentrations of the target gland hormones (Table 170-1). Several tests of pituitary func- tion are listed in Table 170-2.
Table 170-2 Anterior Pituitary Hormone Function Testing RANDOM HORMONE MEASUREMENTS PROVOCATIVE OR OTHER TESTS TARGET HORMONE MEASUREMENT GH (not useful as a random determination except in newborns, and in GH resistance or in pituitary gigantism) Arginine (a weak stimulus) L-Dopa (useful clinically) Insulin-induced hypoglycemia (a dangerous but accurate test) IGF-1, IGFBP3 (affected by malnutrition as well as GH excess)
TSH* TRH FT4 LH, FSH* GnRH (difficult to interpret in prepubertal subjects) Testosterone/estradiol
ACTH, Adrenocorticotropic hormone; CRH, corticotropin-releasing hormone; FSH, follicle-stimulating hormone; FT4, free thyroxine; GH, growth hormone; GnRH, gonadotropin-releasing hormone; GRH, growth hormone-releasing hormone; IGF-1, insulin-like growth factor-1; IGF-BP3, insulin-like growth factor-binding protein 3; L-dopa, L-dihydroxyphenylalanine; LH, luteinizing hormone; TRH, thyrotropin-releasing hormone; TSH, thyroid-stimulating hormone.
*New supersensitive assays allow determination of abnormally low values found in hypopituitarism.
Hypothalamic deficiency leads to a decrease in most pituitary hormone secretions but may lead to an increase in prolactin secretion. Destructive lesions of the pituitary glandor hypothalamus are more common in childhood thanincreased pituitary secretion of various hormones. A craniopharyngioma, a tumor of the Rathke pouch, may descendinto the sella turcica, causing erosion of the bone anddestruction of pituitary and hypothalamic tissue. Acquired hypopituitarism also may result from pituitary infections;from infiltration (Langerhans cell histiocytosis [histiocytosisX], lymphoma, and sarcoidosis); after radiation therapy or trauma to the CNS; and as a consequence of autoimmunity against the pituitary gland.