or more of the hormones it produces. There are
numerous causes for hypopituitarism, some of
which are transient and others that require life-
long HORMONE THERAPYto supplement hormone
deficiencies. Tumors, INFECTION, trauma, and
AUTOIMMUNE DISORDERS are the most common
causes of pituitary damage resulting in hypopitu-
itarism. AMYLOIDOSIS and SARCOIDOSIS may also
cause hypopituitarism. Occasionally the deficien-
cies result from damage to the HYPOTHALAMUS,
which regulates pituitary function, or to the com-
munication between the hypothalamus and the
pituitary gland. Deficiencies may involve any of
the hormones the anterior lobe of the pituitary
gland synthesizes.
The diagnostic path includes BLOOD tests to
measure HORMONElevels. The endocrinologist may
choose to conduct diagnostic imaging procedures
such as COMPUTED TOMOGRAPHY(CT) SCANorMAG-
NETIC RESONANCE IMAGING (MRI) to evaluate the
structural integrity of the involved endocrine
glands. Treatment consists of appropriate hormone
therapy, usually lifelong, to supplement deficient
hormones.
See also HYPERPROLACTINEMIA; POLYGLANDULAR
DEFICIENCY SYNDROME.
hypothalamus A structure of the midbrain that
has both neurologic and endocrine functions,
serving as a bridge between the neurologic system
and the endocrine system. A construction of pri-
marily NERVEcells, the hypothalamus receives and
processes myriad signals from the BRAINand cen-
tral NERVOUS SYSTEMabout vital functions such as
BREATHING, HEART RATE, BLOOD PRESSURE, body tem-
perature (thermoregulation), and fluid balance. In
response to these neurologic signals specific cen-
ters in the hypothalamus synthesize (produce)
numerous hormones that direct the PITUITARY
GLANDto secrete or stop secreting the hormones it
synthesizes or stores.
A dedicated network of BLOODvessels connects
the hypothalamus and the pituitary gland, which
lies beneath the hypothalamus, allowing hypothal-
amic hormones to travel through the blood directly
to the pituitary gland and fostering intimate and
continuous communication between the two struc-
tures. In turn, the hormones the pituitary gland
produces enter the general circulation to direct the
functions of other endocrine glands. Through this
cascading hormonal regulation the hypothalamus
controls, in integration with neurologic processes,
most core functions essential for survival.Hypothalamic Hormones
The hormones the hypothalamus produces are
peptides (amino acid structures) that target spe-
cific cell clusters within the pituitary gland’s two
lobes, acting either to stimulate or inhibit pituitary
gland activity. The hypothalamic hormones are144 The Endocrine System
PITUITARY HORMONE DEFICIENCIESDeficient Hormone Consequences
deficient ADRENOCORTICOTROPIN HORMONE(ACTH) ADRENAL INSUFFICIENCY: HYPOTENSION, HYPOGLYCEMIA, fatigue
deficient GROWTH HORMONE(GH) children: stunted growth
adults: slowed METABOLISM
deficient LUTEINIZING HORMONE(LH) and FOLLICLE- women: cessation of OVULATIONand MENSTRUAL CYCLES, INFERTILITY,
STIMULATING HORMONE(FSH) masculinization
men: HYPOGONADISM, infertility, ERECTILE DYSFUNCTION, feminization
deficient THYROID-STIMULATING HORMONE(TSH) HYPOTHYROIDISM: weight gain, confusion, intolerance to cold,
chronic CONSTIPATION
deficient PROLACTIN BREASTFEEDINGwomen: inability to produce milk