Encyclopedia of Health and Medicine

124 The Endocrine System
See also HYPERCALCEMIA; HYPOKALEMIA; HYPONA-
TREMIA; LESION; SARCOIDOSIS; SICKLE CELL DISEASE.
dopamine A peptide the adrenal medulla of the
ADRENAL GLANDS, the HYPOTHALAMUS, and other
structures in the BRAIN produce. Dopamine functions
in the body as a HORMONE, when synthesized
by the adrenal medulla, and as a NEUROTRANSMITTER
when synthesized by brain structures or NERVE
cells. NOREPINEPHRINE is a dopamine precursor
(substance the body uses as the basis for dopamine
synthesis).
Hormonal dopamine, also called PROLACTIN
release–inhibiting factor (PRIF), is an inhibitory
hormone that acts to prevent the release of the
pituitary hormone prolactin. Dopamine also has
less pronounced inhibitory action for FOLLICLE-
STIMULATING HORMONE (FSH), LUTEINIZING HORMONE
(LH), and THYROID-STIMULATING HORMONE (TSH). The
hypothalamus directs the adrenal medulla to
release dopamine through the neurotransmitter
acetylcholine. As a neurotransmitter, dopamine is
critical to voluntary MUSCLE control and movement,
cognitive function, mood, emotion, and
perceptions of pleasure. Dopamine appears to play
a key role in ADDICTION such as to NARCOTICS and
NICOTINE (cigarette smoking).
Dopamine is also a pharmaceutical DRUG used
to treat CARDIAC ARREST and cardiovascular SHOCK.
When injected intravenously to establish
dopamine levels higher than normal in the bloodstream,
dopamine constricts (narrows) peripheral
BLOOD vessels to direct more blood to critical
organs, intensifies the force of the HEART’s contractions
to increase the amount of blood the heart
pumps, and increases the HEART RATE. The
dopamine precursor levodopa is a treatment for
PARKINSON’S DISEASE (a degenerative neurologic disorder
that results from inadequate dopamine production
in the sections of the brain that control
movement).
For further discussion of dopamine within the
context of the endocrine system’s structure and
function please see the overview section “The
Endocrine System.”
See also EPINEPHRINE.