STEPTRACKERBIOCHEMISTRY + PATHOLOGY | NUTRITION | HIGH-YIELD REVIEW

Minerals & Trace Elements

Small amounts, big enzymes: zinc, copper, selenium, iron, iodine, fluoride and chromium — each with a signature deficiency or excess.

FOCUS ON
Zinc deficiency → poor wound healing, ↓ taste/smell, alopecia, perioral/acral rash (acrodermatitis enteropathica), hypogonadism. Copper deficiency → myelopathy mimicking B12 + anemia/neutropenia (zinc excess, bariatric surgery); excess = Wilson. Selenium → Keshan cardiomyopathy. Iodine → goiter, cretinism. Fluoride excess → mottled teeth. Iron overload → hemochromatosis; deficiency → microcytic anemia.
ELEMENT
ROLE
DEFICIENCY
EXCESS · CLUE
Zinc
Cofactor for > 100 enzymes; zinc-finger transcription factors; immunity, growth, wound healing
Delayed wound healing, dysgeusia, anosmia, alopecia, hypogonadism, ↓ adult hair, acrodermatitis enteropathica (perioral/perianal/acral rash, diarrhea)
Alcohol, Crohn, TPN · excess → copper deficiency
Copper
Lysyl oxidase, cytochrome c oxidase, superoxide dismutase, ceruloplasmin (iron oxidation), dopamine β-hydroxylase
Anemia, neutropenia, myeloneuropathy (looks like B12), hypopigmentation · Menkes (kinky hair)
Bariatric surgery, zinc excess · overload = Wilson
Selenium
Glutathione peroxidase (antioxidant), thyroid deiodinases
Keshan disease (dilated cardiomyopathy), Kashin-Beck (osteoarthropathy), thyroid dysfunction
Low-selenium soils, TPN · excess: garlic breath, nail changes
Iron
Hemoglobin, myoglobin, cytochromes; absorbed as Fe²⁺ in duodenum (DMT1), exported by ferroportin (hepcidin blocks)
Microcytic hypochromic anemia, koilonychia, pica, Plummer-Vinson
Overload: hemochromatosis, transfusions · acute overdose: GI necrosis → acidosis (deferoxamine)
Iodine
Thyroid hormone synthesis
Goiter, hypothyroidism; maternal deficiency → congenital hypothyroidism (cretinism)
Excess → Wolff-Chaikoff (↓ hormone) or Jod-Basedow (hyperthyroid in nodular goiter)
Fluoride
Strengthens enamel (fluorapatite)
Dental caries
Excess → mottled teeth (fluorosis), skeletal fluorosis
Chromium
Enhances insulin action
Glucose intolerance (TPN)
Hexavalent chromium (industrial) → lung cancer
Magnesium
ATP cofactor, PTH secretion, Na⁺/K⁺-ATPase
Hypocalcemia (↓ PTH), refractory hypokalemia, arrhythmias (torsades), tetany
PPIs, diuretics, alcohol, diarrhea · fix Mg before K⁺
Phosphate
ATP, 2,3-BPG, bone
Weakness, rhabdomyolysis, hemolysis, respiratory failure
Refeeding syndrome (6.05)
Calcium
Bone, muscle contraction, coagulation, signaling
Tetany, Chvostek/Trousseau signs, QT prolongation
Excess: stones, bones, groans, psychiatric overtones

Mechanism — zinc excess causes copper deficiency

High zinc intakeSupplements, denture cream
→
Enterocyte metallothionein ↑
→
Copper trapped, shed with cells
→
Copper deficiencyAnemia, neutropenia, myelopathy

The same principle is used deliberately to treat Wilson disease with zinc.

Look-alikes

PRESENTATION
THINK
SEPARATE BY
Dorsal column myelopathy + anemia
B12 or copper deficiency
MMA ↑ only in B12
Dilated cardiomyopathy + malnutrition
Selenium, thiamine
High- vs low-output
Rash around mouth + diarrhea + alopecia
Zinc
↓ Plasma zinc, ↓ ALP

How it's tested

COMMON CONFUSIONCopper deficiency myelopathy mimics B12 deficiency clinically and on MRI — check copper after bariatric surgery or with zinc use.
THE TRAPHypokalemia that won't correct despite KCl → check magnesium.
YOUR APPROACHMatch the organ signature (skin, heart, blood, nerves, thyroid, teeth) to the element, then look for the cause (TPN, surgery, diet, supplement).

If you see… think…

Infant with perioral and acral rash, diarrhea, alopecia → acrodermatitis enteropathica (zinc)
Alcoholic with poor wound healing and loss of taste → zinc deficiency
Post-bariatric patient with B12-like myelopathy, normal B12 → copper deficiency
Dilated cardiomyopathy in a low-selenium region → Keshan disease
Child with goiter and developmental delay in iodine-poor area → iodine deficiency
Mottled brown teeth → fluorosis
Hypokalemia not correcting with KCl → hypomagnesemia
Hypocalcemia that won't correct on PPIs → low Mg (↓ PTH)
Acute iron overdose antidote → deferoxamine
Hormone blocking ferroportin → hepcidin