Webster's New World Medical Dictionary

pituitary dwarfism
See 
dwarfism, pituitary.
pituitary gigantism
See 
gigantism, pituitary.
pituitary gland
An endocrine gland situated at
the base of the brain, which produces hormones
that control other glands and many body functions,
including growth. The pituitary is really two glands:
the anterior pituitary and the posterior pituitary.
Also known as simply the pituitary or hypophysis.
See also 
pituitary, anterior; pituitary, posterior.
pityriasis rosea
A common mild rash of
unknown origin that may last from several weeks to
several months, often beginning with a “herald”
patch, a large single pink patch on the chest or back
and, within a week or so, more pink patches on the
torso, arms, and legs. There may be itching, espe-
cially when overheated. Treatment may include
medications for the itching and soothing lotions or
skin lubricants.
PKD
Polycystic kidney disease.
PKU
Phenylketonuria, a metabolic disease that is
due to the inherited inability to process the essential
amino acid phenylalanine. The biochemical basis of
PKU is complete or near-complete deficiency of the
enzyme phenylalanine hydroxylase. Newborns in
many countries are now routinely screened for PKU
via a blood test. Treatment of PKU involves a special
diet that is low in phenylalanine. The goal is to nor-
malize the levels of phenylalanine and tyrosine in
the blood to prevent brain damage. Failure or lack
of treatment results in profound irreversible mental
retardation, microcephaly, epilepsy, and behavior
problems. If an appropriate diet is not followed
closely, especially during childhood, some impair-
ment is inevitable. PKU is inherited in an autosomal
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PKU
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recessive manner, as are lesser degrees of pheny-
lalanine hydroxylase deficiency. See also 
Guthrie
test; phenylalanine hydroxylase deficiency; PKU,
maternal.
PKU, maternal
The disease phenylketonuria
(PKU) in a pregnant woman whose high blood lev-
els of phenylalanine are dangerous to a developing
fetus. High phe can damage a baby before birth. If
the mother’s PKU is not controlled, the fetus (which
may not have PKU) is at high risk for congenital
heart disease, growth retardation, microcephaly,
and mental retardation. See also 
phenylalanine
hydroxylase deficiency; PKU.
PKU, variant
A form of phenylalanine hydroxy-
lase deficiency that is more mild than classic PKU
and typically causes less intellectual impairment.
placebo
A sugar pill or any other inactive sub-
stance that is given instead of medication. In a con-
trolled clinical trial, one group may be given a
medication and another group a placebo, to learn
whether a difference in treatment response is due to
the medication, the power of suggestion, or other
factors. See also 
placebo response.