TABLE 37-4
Trace Elements Thought to Be Essential in Animals and Humans
*
Deficiency Signs
----------------------------------------------------
Occurrence of
Element*
Function**
Animal
Human
Imbalances in Humans
Arsenic
May be necessary for normal
metabolism o f an amino acid or
protein that influences the
urea cycle.
Impairment o f growth and
reproduction (several species);
heart damage and decreased
plasma triacylglycerol (goats);
plasma amino acid changes.
Not known.
Not known.
Boron*
May act in concert with
magnesium in some aspect of
the metabolism o f calcium,
phosphorous, or magnesium.
Depressed growth and abnormal
bone development when
magnesium or vitamin D
nutrition is marginal.
Not known.
Not known.
Chromium
Potentiates insulin; may be
involved in glucose transport
into the cell.
Relative insulin resistance.
Relative insulin resistance;
impaired glucose tolerance;
elevated serum lipids.
Deficiency known in
malnutrition, total parenteral
nutrition.
Cobalt
Acts as part o f vitamin B ]2.
Anemia; growth retardation in
ruminants.
Only known as vitamin B ,2
deficiency.
Inability to absorb B 12 (pernicious
anemia and other causes);
low B 12 intake from
vegetarian diet.
Copper
Acts as cofactor for oxidative
enzym es, together with iron;
in elastin and collagen cross-
linking; in superoxide dismutase.
Anemia; rupture o f large vessels;
disturbances o f ossification.
Anemia; changes in ossification;
possibly elevated serum
cholesterol.
Deficiencies known in malnutrition,
total parenteral nutrition.
Fluorine§
Influences structure o f teeth,
possibly of bone; has possible
effect on growth; can stimulate
adenylate cyclase.
Dental caries; possible growth
depression; possibly
depressed hematopoiesis
and fertility.
Increased incidence o f dental
caries; possibly increased
likelihood o f osteoporosis.
Deficiency unknown; excess can
cause osteofluorosis and mottled
teeth.
Iodine11’^
Acts as constituent o f thyroid
hormones.
Goiter; depression o f thyroid
function.
Goiter; depression o f thyroid
function; cretinism.
Deficiencies are widespread;
excess leads to thyrotoxicosis.
IronL*
Acts in oxygen transport and
electron transport; part o f
microsomal oxidases (p~450s).
Anemia; growth retardation.
Anemia.
Deficiencies widespread; excess
causes hemochromatosis.
Lithium*
Possibly regulates some endocrine
function; has many similarities
to Na+ and K+; disrupts cAM P-
mediated processes.
Depressed fertility; depressed
growth and longevity.
Not known.
Excess known secondary to use
o f lithium carbonate for
treatment o f mental disorders
(low therapeutic index).
M anganese
Involved in glycosam inoglycan
biosynthesis; as cofactor for
glycosyl transferases; in
Growth depression; bone
deformities; pancreatic j3-cell
degeneration.
Not known.
Deficiency not known; toxicity by
inhalation o f dust.
mitochondrial superoxide
dismutase.
