Trace elements
Each trace metal is the cofactor of one or two enzymes, so its deficiency reads straight off the enzyme: zinc for wound healing and taste, copper for collagen cross-linking and iron transport. Use the absorption site and the exposure before you match symptoms.
Read the absorption site and the exposure first
L6 p.47Trace-element and vitamin questions are easier if you read two clues before the symptom list: where in the gut it is absorbed and what the patient was exposed to. A disease or resection of a specific segment predicts which nutrients fall; an industrial or dietary exposure predicts which metal is in excess.
Clue before symptomRef. · Robbins; absorption sites
| Clue in the stem | What it predicts |
|---|---|
| Terminal ileum resected (Crohn) | B12 and bile-acid (fat-soluble vitamin) loss; zinc loss with short bowel |
| Fat malabsorption (celiac, pancreatitis, cholestasis) | Vitamins A, D, E, K together |
| Gastrectomy / pernicious anemia | B12 (no intrinsic factor); iron |
| Battery factory, old paint, foundry | Lead excess (basophilic stippling) |
| Antifreeze, windshield fluid | Ethylene glycol / methanol (toxic alcohols) |
| House fire | CO and cyanide together |
Terminal ileum resected (Crohn)
- What it predicts
- B12 and bile-acid (fat-soluble vitamin) loss; zinc loss with short bowel
Fat malabsorption (celiac, pancreatitis, cholestasis)
- What it predicts
- Vitamins A, D, E, K together
Gastrectomy / pernicious anemia
- What it predicts
- B12 (no intrinsic factor); iron
Battery factory, old paint, foundry
- What it predicts
- Lead excess (basophilic stippling)
Antifreeze, windshield fluid
- What it predicts
- Ethylene glycol / methanol (toxic alcohols)
House fire
- What it predicts
- CO and cyanide together
Core activity · One Fact Changes
One Fact Changes
1 · The original case
A 37-year-old man has Crohn disease. His terminal ileum was resected. Three years later he takes no supplements. He is examined for a deficiency.
Which deficiency is most likely?
Which fact decided it?
Zinc
L6 p.47Zinc is a cofactor for many metalloenzymes, including collagenase and the matrix enzymes of wound healing, and for taste and smell receptors. Deficiency arises in malabsorption (Crohn disease, repeated small-bowel resection), prolonged parenteral nutrition without zinc, and the inherited disorder acrodermatitis enteropathica.
Zinc deficiencyL6 p.47
| Finding | Why |
|---|---|
| Poor wound healing | Zinc-dependent matrix enzymes and cell proliferation |
| Perioral and perianal (acral) dermatitis, alopecia | Acrodermatitis pattern |
| Dysgeusia (altered taste), anosmia | Zinc in taste/smell receptor function |
| Hypogonadism, growth retardation (children) | Zinc in reproductive and growth pathways |
Poor wound healing
- Why
- Zinc-dependent matrix enzymes and cell proliferation
Perioral and perianal (acral) dermatitis, alopecia
- Why
- Acrodermatitis pattern
Dysgeusia (altered taste), anosmia
- Why
- Zinc in taste/smell receptor function
Hypogonadism, growth retardation (children)
- Why
- Zinc in reproductive and growth pathways
Copper and iron handling
L6 p.47Copper is the cofactor for lysyl oxidase, which cross-links collagen and elastin, and for ferroxidase (ceruloplasmin), which lets iron load onto transferrin. So copper deficiency weakens connective tissue (aortic and arterial walls) and causes a microcytic anemia that iron does not correct, because the iron cannot be mobilized.
Copper deficiencyL6 p.47
| Finding | Enzyme |
|---|---|
| Microcytic anemia (iron-unresponsive); neutropenia | Ferroxidase/ceruloplasmin: iron cannot load onto transferrin |
| Aneurysm, arterial rupture, fragile connective tissue | Lysyl oxidase: collagen/elastin not cross-linked |
| Poor wound healing | Lysyl oxidase in matrix maturation |
Microcytic anemia (iron-unresponsive); neutropenia
- Enzyme
- Ferroxidase/ceruloplasmin: iron cannot load onto transferrin
Aneurysm, arterial rupture, fragile connective tissue
- Enzyme
- Lysyl oxidase: collagen/elastin not cross-linked
Poor wound healing
- Enzyme
- Lysyl oxidase in matrix maturation
Chromium, selenium, iodine and fluoride
L6 p.47The rest of the lecture's trace metalsL6 p.47
| Element | Role | Deficiency |
|---|---|---|
| Chromium | Potentiates insulin | Impaired glucose tolerance, peripheral neuropathy |
| Selenium | Glutathione peroxidase (antioxidant) | Muscle pain and weakness, dilated cardiomyopathy (Keshan disease) |
| Iodine | Thyroid hormone synthesis | Goiter, hypothyroidism |
| Fluoride | Tooth and bone mineral | Dental caries (deficiency); mottled enamel and dense bone (excess) |
Chromium
- Role
- Potentiates insulin
- Deficiency
- Impaired glucose tolerance, peripheral neuropathy
Selenium
- Role
- Glutathione peroxidase (antioxidant)
- Deficiency
- Muscle pain and weakness, dilated cardiomyopathy (Keshan disease)
Iodine
- Role
- Thyroid hormone synthesis
- Deficiency
- Goiter, hypothyroidism
Fluoride
- Role
- Tooth and bone mineral
- Deficiency
- Dental caries (deficiency); mottled enamel and dense bone (excess)
Knowledge check · 6.6
Answer, read why, and try again whenever you like. Answers are kept in both study modes.
- Q1Zinc deficiencyCh. VI cases p.10L6 p.47
A 34-year-old woman with Crohn disease who has had several segmental small-bowel resections develops hair loss, perioral bullous plaques, and food that tastes bland.
Which deficiency best explains this?
- Q2Zinc deficiency (Chapter II crossover)Ch. II cases p.10L6 p.47
A 38-year-old man with Crohn disease and several small-bowel resections has hair loss, a rash around the mouth, and a persistent metallic taste.
Which element is he most likely deficient in?
- Q3Copper and lysyl oxidaseL6 p.47Ref. · Robbins; Menkes, lysyl oxidase
An infant fed only an unsupplemented formula has a microcytic anemia that does not respond to iron, brittle depigmented hair, and a tortuous aorta on imaging.
Which enzyme defect best explains the vascular fragility?