Vitamins and Minerals Flashcards
IRON
Absorption:
- Takes place in upper small intestine
- About 10% of dietary iron absorbed
- Fe2+ (ferrous iron) much better absorbed than Fe3+ (ferric iron)
- Absorption is regulated according to body’s need
- Absorption is increased by vitamin C, gastric acid
- Absorption is decreased by proton pump inhibitors, tetracycline, gastric achlorhydria and tannin (found in tea)
Distribution in body:
- total body iron = 4g
- haemoglobin = 70%
- ferritin and haemosiderin = 25%
- myoglobin = 4%
- plasma iron = 0.1%
Transport:
Carried in plasma as Fe3+ bound to transferrin
Storage:
Stored in tissues as FERRITIN
Excretion:
Lost via intestinal tract following DESQUAMATION
Pellagra
Pellagra is a rare condition in the United Kingdom but it is seen in patients with carcinoid syndrome. It is caused by a deficiency in vitamin B3, (Niacin) and classically presents as the ‘4 Ds’ dermatitis, dementia, diarrhoea and death. Niacin can be absorbed through the diet or converted in vivo from tryptophan. Patients with carcinoid syndrome are at increased risk as tryptophan stores are metabolised to serotonin.
Pellagra is a caused by nicotinic acid (niacin) deficiency. The classical features are the 3 D’s - dermatitis, diarrhoea and dementia, also Depression
Pellagra may occur as a consequence of isoniazid therapy (isoniazid inhibits the conversion of tryptophan to niacin) and it is more common in alcoholics.
Features dermatitis (brown scaly rash on sun-exposed sites - termed Casal's necklace if around neck) diarrhoea dementia, depression death if not treated
Pellagra occurs primarily in countries such as India and China, in which corn is a staple food. In the UK it is uncommon, and largely seen in patients with alcohol dependency or anorexia nervosa. Niacin is absorbed from foods such as beans and eggs and is also converted from amino acid tryptophan. Pellagra may manifest in carcinoid syndrome, in which tryptophan is converted to serotonin.
Beri-Beri
Beriberi is caused by thiamine deficiency and typically causes:
- a peripheral neuropathy
- high-output cardiac failure
- associated with weight loss.
Pellagra - Example Question
A 58 year-old man is referred to the clinic with chronic diarrhoea and episodes of facial flushing. A computed tomography scan of her chest and abdomen reveal she has a neuroendocrine carcinoma of the appendix, causing carcinoid syndrome.
She refuses treatment and presents six months later having been referred by a neurologist as having early onset dementia and a rapidly evolving photosensitive rash on her trunk and upper arms.
Which of the following is the most likely diagnosis?
Systemic lupus erythematosus Herpes Zoster infection > Pellagra Wernicke-Korsakoff syndrome Porphyria
The most likely diagnosis in this case is pellagra, a vitamin deficiency disease most frequently caused by a chronic lack of niacin (vitamin B3). In carcinoid syndrome, neuroendocrine tumours along the GI tract use tryptophan as the source for serotonin production, which limits the available tryptophan for niacin synthesis, thus carcinoid syndrome produces a niacin deficiency.
Vitamin C
= water soluble vitamin
Functions:
- antioxidant
- collagen synthesis - acts as a cofactor for enzymes that are required for the hydroxylation of proline and lysine in the synthesis of collagen
- facilitates iron absorption
- cofactor for norepinephrine synthesis
Scurvy
Vitamin C deficiency = SCURVY
Leads to defective collagen synthesis > capillary fragility (tendency to bleed) and poor wound healing
Features:
- gingivitis
- loss of teeth
- epistaxis
- poor wound healing
- bleeding from gums
- haematuria
- general malaise
Vitamin D Resistant Rickets
= X-linked dominant condition
Usually presents in infancy with FAILURE TO THRIVE
Caused by impaired phosphate reabsorption in renal tubules
Features:
- N serum calcium
- Low phosphate
- Elevated ALP
- X-ray changes: cupped metaphyses with widening of epiphyses
Diagnosis:
- Demonstrated by increasing urinary phosphate
Mx:
- High dose Vit D supplements
- Oral phosphate supplements
Vitamin C and Scurvy
Vitamin C deficiency (scurvy)
Vitamin C is found in citrus fruits, tomatoes, potatoes, Brussel sprouts, cauliflower, broccoli, cabbage and spinach. Deficiency leads to impaired collagen synthesis and disordered connective tissue. It is associated with severe malnutrition as well as drug and alcohol abuse, and those living in poverty with limited access to fruits and vegetables.
Symptoms and signs include:
Follicular hyperkeratosis and perifollicular haemorrhage
Ecchymosis (a discoloration of the skin resulting from bleeding underneath)
Gingivitis with bleeding and receding gums
Sjogren’s syndrome
Arthralgia
Oedema
Impaired wound healing
Generalised symptoms such as weakness, malaise, anorexia and depression
Scurvy Diagnosis - Example Question
A 42-year-old man presents to the emergency department due to bleeding from hair follicles on his head. He has also noticed that he has been off his food and losing weight. He is currently homeless after having been made redundant from his job one year ago. He is alcohol dependent with 30-units per week of hard liquor. He is not confused.
He has a past medical history of tuberculosis, for which he completed treatment six months. This treatment finished two months ago. On examination, he appears unkempt with poor oral hygiene and gingivitis. He has global muscle weakness rated at 4+/5 on the MRC scale. There is no sensory impairment. What is the most likely diagnosis?
Pellagra > Scurvy Beriberi Wernicke-Korsakoff syndrome Recurrence of tuberculosis
The correct answer is scurvy. He is a homeless and alcohol-dependent patient who is very likely to have a very poor diet. The combination of bleeding hair follicles and gingivitis is highly suggestive of vitamin C (ascorbic acid) deficiency. Pellagra is associated with diarrhoea and dementia. Beriberi can be associated with peripheral neuropathy with sensory involvement, or heart failure and oedema. Neither of these cases is described here. The classical triad of nystagmus, ophthalmoplegia and ataxia with confusion is not described, making Wernicke-Korsakoff syndrome less likely. The absence of a cough, haemoptysis and night sweats makes TB recurrence less likely.
Vitamin B1 - Thiamine
Vitamin B1 (thiamine)
Thiamine is a water soluble vitamin of the B complex group. One of it’s phosphate derivates, thiamine pyrophosphate (TPP), is a coenzyme in the following enzymatic reactions:
pyruvate dehydrogenase complex
pyruvate decarboxylase in ethanol fermentation
alpha-ketoglutarate dehydrogenase complex
branched-chain amino acid dehydrogenase complex
2-hydroxyphytanoyl-CoA lyase
transketolase
Thiamine is therefore important in the catabolism of sugars and aminoacids. The clinical consequences of thiamine deficiency are therefore seen first in highly aerobic tissues such as the brain (Wenicke-Korsakoff syndrome) and the heart (wet beriberi).
Causes of thiamine deficiency:
alcohol excess
malnutrition
Conditions associated with thiamine deficiency:
Wernicke’s encephalopathy: nystagmus, ophthalmoplegia and ataxia
Korsakoff’s syndrome: amnesia, confabulation
dry beriberi: peripheral neuropathy
wet beriberi: dilated cardiomyopathy
Vitamin B1 - Thiamine Deficiency: Example Question
A 58-year-old man with long-standing Crohn’s disease presents with a 1-year history of fatigue. In the last month, he has developed weakness and muscle pain. He also reports a number of trips and falls.
On examination, he is thin and pale. Heart rate is 85 beats per minute and blood pressure is 130/80 mmHg. His chest is clear and heart sounds normal, with no added sounds. His abdomen is soft and has a laparotomy scar. Neurological examination reveals bilateral foot drop, with reduced ankle jerks. He has widespread muscle wasting and calf fasciculations. He has reduced pin-prick sensation to mid shin.
Blood tests show:
Hb 144 g/l
Platelets 195 * 109/l
WBC 6.3* 109/l
Na+ 137 mmol/l K+ 4.5 mmol/l Urea 7 mmol/l Creatinine 91 µmol/l Corrected calcium 2.5 mmol/l HbA1c 45 mmol/mol
What is the diagnosis?
Diabetes mellitus Motor neurone disease > Beriberi Pellagra Friedreich's ataxia
This patient is malnourished due to Crohn’s disease. Chronic thiamine deficiency has led to his fatigue and neurological symptoms. Beriberi typically presents with fatigue, nausea and abdominal pain. If left untreated it can progress, leading to peripheral neuropathy, muscle pain and congestive cardiac failure. Diagnosis is usually made after a response to parenteral thiamine and symptoms tend to improve rapidly with treatment.
Diabetes mellitus and pellagra can cause a peripheral neuropathy, however, this man has a normal HbA1c. Pellagra presents with confusion, rash and diarrhoea. The sensory findings rule out motor neurone disease. Friedrich’s ataxia is an autosomal recessive disorder that typically presents in much younger patients.
Alcohol dependency, renal dialysis and a diet high in milled rice are also risk factors for Beriberi.
Vitamin D Deficiency and Mx
Vitamin D deficiency versus insufficiency
Description > Serum levels > Treatment
Adequate vitamin D
>50 nmol/L
Dietary recommendations
Insufficient vitamin D
30-50 nmol/L
maintenance dose vitamin D
Deficient vitamin D
<30 nmol/L
loading dose vitamin D
Example Question:
A 26-year-old man is reviewed in gastroenterology clinic. He is known to have Crohn’s disease which has been stable over the last six months and not required any recent steroids or hospital admissions. Routine blood tests demonstrate a vitamin D level at 22 nmol/L. All other blood tests, including calcium, are within normal range. What is the most appropriate management plan?
No treatment needed Dietary advise only Maintenance dose vitamin D > Loading dose vitamin D Combined calcium and vitamin D
The correct answer is loading dose vitamin D. He has a serum concentration <30 nmol/L and therefore has vitamin D deficiency, likely secondary to his Crohn’s disease. He, therefore, needs a loading dose of vitamin D. As calcium levels are normal there is no current indication for supplementation.
Osteomalacia
Osteomalacia
Basics
normal bony tissue but decreased mineral content
rickets if when growing
osteomalacia if after epiphysis fusion
Types vitamin D deficiency e.g. malabsorption, lack of sunlight, diet renal failure drug induced e.g. anticonvulsants vitamin D resistant; inherited liver disease, e.g. cirrhosis
Features
rickets: knock-knee, bow leg, features of hypocalcaemia
osteomalacia: bone pain, fractures, muscle tenderness, proximal myopathy
Investigation
low calcium, phosphate, 25(OH) vitamin D
raised alkaline phosphatase
x-ray: children - cupped, ragged metaphyseal surfaces; adults - translucent bands (Looser’s zones or pseudofractures)
Treatment
calcium with vitamin D tablets
Pellagra - Example Question
A 45-year-old woman is admitted with hallucinations. She has a long history of alcohol dependency and is being treated by her GP for hypothyroidism. Further questioning of her husband reveals a 3-month history of diarrhoea, difficulty swallowing and an itchy rash on her arms. Prior to this she had been irritable and suffered from regular bouts of vomiting.
The examination is limited as the patient is aggressive . There is a pigmented, scaly rash on her arms and neck. Heart sounds are normal, her chest is clear and her abdomen soft. Neurological examination reveals generalised weakness.
Blood tests show:
Hb 142 g/l
Platelets 200 * 109/l
WBC 5.3 * 109/l
Na+ 140 mmol/l
K+ 4.2 mmol/l
Urea 6 mmol/l
Creatinine 84 µmol/l
TSH 4.0 U/mL
Free T3 3.1 pg/mL
Free T4 1.5 ng/L
What is the most likely diagnosis?
Beriberi Thyroxine toxicity Systemic lupus erythematosus (SLE) > Pellagra Darier's disease
This lady has pellagra, caused by niacin (vitamin B3) deficiency. It occurs primarily in countries such as India and China, in which corn is a staple food. In the UK it is uncommon, and largely seen in patients with alcohol dependency or anorexia nervosa. Niacin is absorbed from foods such as beans and eggs and is also converted from amino acid tryptophan. Pellagra may manifest in carcinoid syndrome, in which tryptophan is converted to serotonin.
Over-treatment or deliberate overdose of thyroxine could cause some of this patient’s symptoms, but her thyroid function tests are normal. SLE and Darier’s disease both cause a light-sensitive rash, but would not cause the gastrointestinal symptoms. Cognitive disturbance may be seen in SLE.
Pellagra is distinguished from beriberi by the presence of a rash and gastrointestinal symptoms. Like beriberi, it can lead to confusion and memory deficits. Alcoholic patients may, of course, present with both. Other signs include dilated cardiomyopathy, oesophagitis and ataxia.
Osteomalacia - Example Question
A 28-year-old woman presents to the gastroenterology clinic for review. She has been diagnosed with coeliac disease some 2 years earlier, and has been suffering from severe tiredness, muscle aches and proximal weakness for the past few months. On examination her blood pressure is 112/70 mmHg, pulse is 75 beats per minute and regular. You confirm proximal muscle weakness.
Investigations
Ca++ 2.0 mmol/l
Alkaline phosphatase 275 IU/l
Which of the following is the most useful next investigation?
CK Parathyroid hormone > Vitamin D Muscle biopsy Electromyography
Coeliac disease is known to interfere with absorption of fat soluble vitamins, including vitamin D, and the low calcium and elevated alkaline phosphatase, coupled with symptoms of proximal myopathy fits with a diagnosis of osteomalacia. Vitamin D levels are therefore the next investigation of choice.
CK and muscle biopsy are indicated for possible inflammatory myositis, and the limited proximal weakness seen here, coupled with low calcium is much more consistent with osteomalacia. Parathyroid hormone may be elevated, but this is secondary to low vitamin D and calcium. Electromyography is most useful for assessment of motor neuropathy, which doesn’t fit with the painful proximal muscle weakness seen here.
