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Questions and Answers
Which trace element is primarily stored by metallothionein?
What is the dietary requirement for copper per day?
Which condition is associated with a deficiency in copper?
In which food sources is copper predominantly found?
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Which of the following is NOT a function of copper in the body?
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What role does ceruloplasmin play in relation to iron?
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What is the method used for the laboratory determination of trace elements?
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Which disease is characterized by a decreased ceruloplasmin level?
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Which organ is NOT primarily affected by Wilson's Disease due to copper accumulation?
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What is the method of choice for measuring serum copper levels?
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Which of the following zinc-containing proteins is involved in RNA synthesis?
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What clinical manifestation is associated with Wilson's Disease?
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What is the serum reference interval for males regarding copper levels?
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Which trace element plays a crucial role in insulin synthesis and action?
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Which of the following factors does NOT influence zinc laboratory determination?
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Acrodermatitis enteropathica is a rare disorder associated with which trace element?
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What method is considered the method of choice for measuring zinc in body fluids?
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What is the plasma reference value for zinc in μg/dL?
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Which statement about iron metabolism is correct?
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Which of the following is NOT a direct measurement method for assessing iron levels?
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What role does iron play in the immune system?
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What is the cause of increased serum ferritin levels?
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How is serum iron measured?
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What percentage of dietary iron is typically absorbed by the body?
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Study Notes
Trace Elements
- Trace elements are minerals present in tiny amounts, but are crucial for physiological functions.
- Roles: Enzyme function, hormone production, overall cellular health
- Associated with: enzymes and proteins
- Deficiency consequences: Impair biochemical and functional processes, correctable with replacement.
- Lab determination: Needs anti-coagulated blood, due to low concentration and ubiquity.
- Atomic Absorption Spectrophotometry is used to prevent contamination.
Copper
- Third most abundant trace element.
- Dietary sources: Shellfish, legumes, nuts, liver.
- Dietary requirement: 1.5-3.0 mg/day
- Functions: Cellular respiration, DNA/RNA reproduction, maintains cell membrane integrity, sequestering free radicals.
- Distribution: Highest concentration in liver.
- Copper-containing proteins: Ceruloplasmin, albumin-bound, transcuperin.
- Ceruloplasmin: a-2 globulin, functions as a ferroxidase enzyme (NOT a transporter, copper is not exchangeable).
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Clinical correlation:
- Copper deficiency: Seen in premature infants, undernourished children, adults with osteoporosis and CVD. Menke's disease (kinky hair syndrome) with decreased ceruloplasmin levels and low copper concentration in hair.
- Copper toxicity: Increased copper in tissue and serum. Manifestations include hypotonia, acute copper poisoning (from fungicides), and Wilson's disease (genetic copper accumulation).
- Wilson's disease: Inability to metabolize copper, leading to accumulation in the liver, brain, and cornea. Leads to neurologic disorders, liver dysfunction, and Kayser-Fleischer rings in cornea.
- Laboratory methods: Serum or urine are used for detection. Measured by Atomic Absorption Spectroscopy (method of choice) or colorimetric methods.
- Ceruloplasmin measurement: Photometric methods or immunochemical methods like nephelometry.
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Reference interval:
- Serum Copper: Male: 70-140 ug/dL (11-22 umol/L), Female: 80-155 ug/dL (13-14 umol/L).
- Ceruloplasmin: 23-50 mg/dL.
Zinc
- Second most abundant trace element.
- Roles/Functions: Cofactor for over 300 enzymes, essential for protein and nucleic acid synthesis, vital for insulin synthesis and action.
- Zinc-containing proteins: Carbonic anhydrase, alkaline phosphatase, DNA & RNA polymerase, carboxypeptidase, alcohol dehydrogenase, superoxide dismutase.
- Metabolism and Distribution: Absorbed in the duodenum, transferred to portal blood by metallothionein. Bound to albumin and a-2 macroglobulin in blood.
- Zinc stores: Muscle and bones (slow turnover, 300-day half-life), readily mobilized from the liver (metallothionein-bound, 2-week half life).
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Clinical significance:
- Zinc deficiency: Common in patients with diabetes mellitus, alcohol abuse, malabsorption syndromes, liver and kidney diseases, and acrodermatitis enteropathica (rare autosomal recessive disorder with impaired intestinal zinc absorption and transport).
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Laboratory Determination:
- Factors to consider: Diurnal variation (higher in AM), postprandial variation (higher when fasting), serum values 10% higher than plasma, RBC zinc 10 times higher than plasma zinc.
- Methods: Method of choice: Atomic Absorption Spectroscopy (Flame Atomic Absorption for body fluids, ICP-MS for reference testing).
- Plasma reference value: 70-120 ug/dL (10.7-18.4 umol/L).
Iron
- Most abundant trace element: 40-50 mg iron/kg body weight.
- Roles/Functions: Essential for iron-containing proteins: hemoglobin, collagen, tyrosinase, catecholamines. Important for cell-mediated immunity (modulates lymphocyte proliferation/differentiation), and affects macrophage immune potential.
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Distribution:
- Hemoglobin in RBCs
- Ferritin and hemosiderin (iron stores)
- Body tissues (myoglobin, non-heme enzymes)
- Iron bound to transferrin
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Metabolism and regulation:
- Dietary iron (ferrous form) absorption is facilitated by ascorbic acid, other reducing agents, and acidic stomach pH. Only 5-10% absorption rate.
- Transferrin: Glycoprotein synthesized in the liver, transports iron with high affinity for ferric ion (not ferrous).
- Ferritin: Found in all cells, stored form of iron. Measured to diagnose IDA (iron deficiency anemia). Increased serum ferritin may occur due to fever, acute infections, rheumatoid arthritis, and viral hepatitis.
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Laboratory methods:
- Direct measurements: Quantitative, specific, sensitive, involve invasive procedures (quantitative phlebotomy, bone marrow/liver biopsy).
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Indirect measurements:
- Serum iron: Measured by colorimetric methods, AAS.
- Serum transferrin: Measured by direct immunoassay or TIBC (maximum binding capacity of transferrin).
- Transferrin ratio: Ratio of plasma to TIBC to indicate iron saturation.
- Serum ferritin: Measured by immunoradiometric assay, ELISA, immunofluorometric assay.
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Description
This quiz explores the significance of trace elements, particularly copper, in human physiology. It covers their roles, dietary sources, and functions within the body. Additionally, it discusses the implications of deficiency and the methods used for determination in a lab setting.
