Comprehensive Urine Elements Profile - Timed

Aluminium is absorbed through the gastrointestinal tract, respiratory system, and skin. The kidneys are the primary route of excretion, and urinary concentration reflects recent exposure or mobilisation from tissue stores. Aluminium has no known physiological role in humans and accumulates in bone, brain, and liver when clearance is impaired.

Elevated urinary aluminium may indicate occupational or environmental exposure, use of aluminium-containing antacids or antiperspirants, or impaired renal clearance. Very high levels have been associated with dialysis encephalopathy and osteomalacia in patients with chronic kidney disease.

Arsenic exists in inorganic (highly toxic) and organic forms (e.g., arsenobetaine from seafood, which is non-toxic). Inorganic arsenic is metabolised to monomethylarsonic and dimethylarsinic acids, excreted in urine. Total urinary arsenic includes all forms; speciation is required to assess toxicity.

Elevated inorganic arsenic reflects exposure from contaminated water, industrial sources, or certain foods. Chronic exposure is linked to skin lesions, peripheral neuropathy, cardiovascular disease, and increased cancer risk. Seafood consumption raises total arsenic without toxicity.

Cadmium is absorbed via inhalation (tobacco smoke, occupational) and ingestion (contaminated crops). It accumulates in the kidneys with a biological half-life of decades. Urinary cadmium reflects body burden and is the preferred biomarker for chronic exposure.

Elevated urinary cadmium indicates chronic exposure, primarily from smoking or occupational sources. It is nephrotoxic, causing tubular dysfunction and, at high levels, osteomalacia (itai-itai disease). Lower-level chronic exposure is associated with reduced bone density and increased fracture risk.

Mercury exists as elemental (vapour from amalgam, occupational), inorganic (salts), and organic (methylmercury from fish). Urinary mercury primarily reflects elemental and inorganic forms; methylmercury is excreted mainly in faeces and hair. Renal tubular cells are a target of inorganic mercury toxicity.

Elevated urinary mercury suggests exposure to elemental vapour (dental amalgam, occupational) or inorganic salts. Chronic exposure can cause renal tubular damage, tremor, and neuropsychiatric effects. Methylmercury (fish) is better assessed via blood or hair.

Lead accumulates in bone with a half-life of years to decades and is slowly released into blood. Urinary lead reflects recent blood lead and, to a degree, bone stores. It is not the first-line biomarker for lead exposure — blood lead is preferred — but urine is sometimes measured after chelation to assess mobilisable burden.

Elevated urinary lead may indicate recent exposure or bone mobilisation. Lead is neurotoxic, haematotoxic, and nephrotoxic, with no safe threshold in children. In adults, chronic low-level exposure is associated with hypertension, renal impairment, and cognitive decline.

Iodine is an essential component of thyroid hormones. More than 90 per cent of dietary iodine is excreted in urine, making urinary iodine the biomarker of choice for assessing population iodine status. Spot urine samples show high day-to-day variation; timed or 24-hour collections improve precision.

Urinary iodine assesses adequacy rather than toxicity. Low values (<100 µg/L) suggest iodine insufficiency, a cause of goitre and hypothyroidism. High values (>300 µg/L) can reflect excessive supplementation or exposure and, in susceptible individuals, precipitate thyroid dysfunction.

Selenium is an essential trace element, a component of selenoproteins including glutathione peroxidases and thioredoxin reductases. Urinary excretion increases with intake and reflects recent exposure rather than tissue stores. Serum selenium is the preferred marker of nutritional status.

Urinary selenium correlates with dietary intake and supplementation. Deficiency is rare in developed countries but can cause cardiomyopathy (Keshan disease) and skeletal myopathy. Excess selenium (chronic intake >400 µg/day) can cause selenosis with hair loss, nail changes, and neurological symptoms.

Cobalt is a component of vitamin B12 but has no independent physiological role in ionic form. Urinary cobalt reflects recent exposure from diet, occupational sources (hard-metal industry), or release from metal-on-metal hip prostheses.

Elevated urinary cobalt may indicate occupational exposure, failing orthopaedic implants, or excessive supplementation. High levels can cause cardiomyopathy, polycythaemia, and thyroid dysfunction. Routine monitoring is not warranted except in specific exposure scenarios.

Creatinine is a metabolite of muscle creatine, excreted at a relatively constant rate. Urinary creatinine concentration is used to normalise spot urine measurements, correcting for hydration status and urine flow. Very low or high creatinine may indicate over- or under-collection, or altered muscle mass.

Creatinine adjustment improves comparability of spot urine samples. Values outside the reference range prompt consideration of collection error, extremes of hydration, or, rarely, significant muscle wasting or renal disease.