Effects of Deficiency of Vitamin K

1. Functions of Vitamin K

1. The most important function of vitamin K is that it acts as a cofactor for the post-translational γ-carboxylation of glutamate residues in clotting factors II (prothrombin), VII, IX, X, and proteins C and S. This modification enables calcium binding and proper blood coagulation. A decrease in plasma prothrombin level is seen in vitamin K deficiency. This results in formation of inactive clotting precursors known as PIVKA (Protein Induced by Vitamin K Absence).
2. It also appears to have a role in the electron transport system, because its structure is similar to coenzyme Q. In the plant kingdom, vitamin K1 (phylloquinone) is an essential component of the photosynthetic electron transport process in Photosystem I.

1.1 Vitamin K exists in different forms:

• Vitamin K1 (phylloquinone) – found in green leafy vegetables
• Vitamin K2 (menaquinone) – produced by intestinal bacteria and found in fermented foods
• Vitamin K3 (menadione) – synthetic form, not commonly used clinically due to toxicity

1.2 Vitamin K cycle and mechanism:

Vitamin K functions through the vitamin K cycle, in which it is continuously regenerated after participating in carboxylation reactions. This cycle involves vitamin K epoxide reductase (VKOR), which is also the target of anticoagulant drugs like warfarin. Inhibition of this enzyme leads to a functional vitamin K deficiency.

1.3 Bone and vascular roles:

Vitamin K is also important for bone and vascular health, as it activates:

• Osteocalcin (important for bone mineralization)
• Matrix Gla protein (MGP) (prevents vascular calcification)

2. Effects of Vitamin K Deficiency

Vitamin K deficiency leads to impaired synthesis of functional clotting factors due to defective γ-carboxylation. This results in reduced coagulation ability and a bleeding tendency.

There is an increase in prothrombin time (PT) and International Normalized Ratio (INR), indicating deficiency of clotting factors. Clotting time is prolonged, and there is a tendency to bleed from minor trauma.

Bleeding commonly occurs from the gastrointestinal tract, urinary tract, and uterus.

2.1. Clinical Manifestations

1. The earliest laboratory abnormality is prolonged prothrombin time (PT) and increased INR due to factor VII having the shortest half-life.
2. Activated partial thromboplastin time (aPTT) may remain normal in early stages.
3. Platelet count remains normal, which is an important distinguishing feature from thrombocytopenia.
4. Severe deficiency may cause ecchymosis, epistaxis, hematuria, and intracranial hemorrhage.
5. Presence of PIVKA proteins reflects functional vitamin K deficiency.

3. Conditions Associated with Vitamin K Deficiency

Many conditions are associated with vitamin K deficiency and lead to bleeding tendencies by producing hypoprothrombinemia:

1. Faulty absorption of vitamin K due to lack of bile, as occurs in obstructive jaundice and biliary fistula. Water-soluble preparations of vitamin K can still be absorbed in the absence of bile salts.
2. Diarrheal diseases such as sprue, celiac disease, and ulcerative colitis interfere with absorption of vitamin K. Prolonged use of mineral oil (liquid paraffin) also reduces absorption.
3. Administration of broad-spectrum antibiotics reduces intestinal flora and decreases endogenous synthesis of vitamin K2.
4. In newborn babies, especially premature infants: Vitamin K does not easily cross the placenta, and the neonatal intestine is sterile, so no bacterial synthesis occurs. This leads to physiological hypoprothrombinemia of the newborn. This can result in hemorrhagic disease of the newborn (VKDB) if not prevented. Routine vitamin K prophylaxis is therefore given at birth.
5. Administration of drugs with anti-vitamin K activity: Warfarin and related anticoagulants inhibit VKOR enzyme, leading to reduced regeneration of active vitamin K. Large doses of salicylates may also interfere with vitamin K metabolism. Vitamin K1 (phytonadione) is used to reverse these effects. Vitamin K3 (menadione) is not used clinically due to toxicity.

4. Additional Risk Factors

1. Long-term therapy with warfarin (vitamin K antagonist anticoagulant)
2. Severe malnutrition or very low dietary intake
3. Fat malabsorption syndromes (chronic pancreatitis, cystic fibrosis, short bowel syndrome)

5. Liver Disease Association

Extensive liver disease also results in low plasma prothrombin levels. Vitamin K administration may not correct this condition because liver cells are unable to synthesize clotting factors.

In liver disease, both synthesis of clotting factors and utilization of vitamin K–dependent proteins are impaired, so response to vitamin K may be minimal or absent.

6. Human Requirements

Not fully established historically, but modern estimates suggest a requirement of approximately 90–120 µg/day in adults, depending on sex and physiological status. Normally, dietary intake is sufficient, and intestinal bacterial synthesis also contributes. Storage of vitamin K in the body is limited.

7. Nutrition

1. Vitamin K is found mainly in green leafy vegetables (K1) and fermented foods (K2).
2. Gut microbiota contributes significantly to menaquinone (K2) production, but dietary intake is still important.
3. Deficiency from diet alone is rare in healthy adults.
4. Fat is required for optimal absorption since vitamin K is fat-soluble.

8. Distinction between Vitamin K Deficiency vs Liver Disease vs Warfarin

Vitamin K–dependent coagulation abnormalities can occur in three major clinical settings: true vitamin K deficiency, liver disease, and warfarin therapy. Although all three present with similar bleeding tendencies and prolonged prothrombin time (PT), the underlying mechanisms and response to treatment are different.

1. Vitamin K Deficiency

In vitamin K deficiency, the liver is structurally normal, but there is a lack of available vitamin K required for γ-carboxylation of clotting factors.

Key features:

• Decreased functional vitamin K availability
• Reduced activation of factors II, VII, IX, X
• Reduced proteins C and S
• Increased PT/INR
• Normal liver function tests

Response to vitamin K:

✔ Rapid correction after vitamin K administration

Because the liver can still synthesize clotting factors, providing vitamin K restores normal function.

2. Liver Disease

In liver disease, the problem is not vitamin K deficiency but failure of hepatocytes to synthesize clotting factors.

Key features:

• Impaired synthesis of clotting factors (II, VII, IX, X)
• Reduced production of proteins C and S
• Decreased albumin and other hepatic proteins
• Prolonged PT and often aPTT in advanced disease
• Abnormal liver function tests (ALT, AST, bilirubin elevated)

Response to vitamin K:

✖ Minimal or no response to vitamin K

Because damaged liver cells cannot synthesize clotting factors even if vitamin K is provided.

3. Warfarin Therapy

Warfarin causes a functional vitamin K deficiency by inhibiting vitamin K epoxide reductase (VKORC1), which prevents recycling of active vitamin K.

Key features:

• Normal liver function
• Inhibition of vitamin K recycling
• Reduced activation of vitamin K–dependent clotting factors
• Prolonged PT/INR (used for monitoring therapy)

Response to vitamin K:

✔ Reversible with vitamin K administration (phytonadione)

Warfarin effect can be partially or completely reversed depending on dose and clinical urgency.

Key Distinguishing Summary

• Vitamin K deficiency → lack of substrate → correctable
• Liver disease → inability to synthesize clotting factors → not correctable
• Warfarin → enzyme inhibition → pharmacologically reversible

9. Epidemiology/Risk Populations

Vitamin K deficiency is relatively uncommon in healthy adults due to dietary availability and intestinal bacterial synthesis. However, certain populations are at significantly increased risk due to impaired intake, absorption, or utilization.

1. Neonates and Infants (Highest Risk Group)

Newborns are the most vulnerable group due to:

• Very low placental transfer of vitamin K
• Sterile intestine at birth (no bacterial synthesis of K2)
• Low vitamin K content in breast milk

Clinical importance:

• Risk of hemorrhagic disease of the newborn (VKDB)
• Can lead to intracranial hemorrhage and life-threatening bleeding if untreated

2. Patients with Malabsorption Disorders

Any condition affecting fat absorption can reduce vitamin K uptake.

High-risk conditions:

• Obstructive jaundice
• Cholestasis and biliary fistula
• Celiac disease
• Crohn’s disease
• Short bowel syndrome
• Chronic pancreatitis
• Cystic fibrosis

3. Patients on Long-Term Antibiotics

Broad-spectrum antibiotics reduce intestinal bacterial flora, especially those producing vitamin K2.

Risk mechanism:

• Decreased gut synthesis of menaquinone
• Especially significant in prolonged hospital treatment

4. Patients on Anticoagulant Therapy

• Long-term warfarin use is a major iatrogenic cause
• Requires careful INR monitoring
• Over-anticoagulation increases bleeding risk

5. Patients with Liver Disease

• Cirrhosis, hepatitis, and severe hepatic dysfunction
• Reduced synthesis of clotting factors
• Poor response to vitamin K in advanced disease

6. Malnourished and Elderly Individuals

• Poor dietary intake of green vegetables
• Reduced absorption efficiency with age
• Often combined with chronic illness or polypharmacy

7. Other At-Risk Groups

• Prolonged use of mineral oil (interferes with fat-soluble vitamin absorption)
• Critically ill ICU patients with poor nutritional intake
• Patients receiving parenteral nutrition without supplementation

10. Prevention Section

Prevention of vitamin K deficiency is based on ensuring adequate intake, maintaining gut synthesis, and providing prophylaxis in high-risk groups.

1. Neonatal Prevention (Most Important Clinical Step)

Routine prophylactic administration of vitamin K at birth is standard practice worldwide.

Purpose:

• Prevent hemorrhagic disease of the newborn (VKDB)

Method:

• Single intramuscular injection of vitamin K1 (phytonadione) at birth

Importance:

• Highly effective in preventing early and late neonatal bleeding
• Significantly reduces risk of intracranial hemorrhage

2. Dietary Prevention

Adequate intake of vitamin K–rich foods is essential.

Sources:

• Green leafy vegetables (spinach, kale, cabbage)
• Fermented foods (for K2)
• Animal products in small amounts

3. Maintaining Gut Flora

Normal intestinal microbiota plays an important role in vitamin K2 synthesis.

Prevention strategies:

• Avoid unnecessary prolonged antibiotic use
• Restore gut flora when possible (dietary support or probiotics in some cases)

4. Prevention in Malabsorption States

In patients with chronic fat malabsorption:

• Supplementation of fat-soluble vitamins may be required
• Water-soluble vitamin K preparations can be used when absorption is impaired

5. Clinical Monitoring in High-Risk Patients

• Regular PT/INR monitoring in warfarin therapy
• Liver function monitoring in hepatic disease
• Nutritional assessment in chronic illness

6. Drug Safety Awareness

• Avoid overdose of anticoagulants
• Monitor drug interactions that affect vitamin K metabolism (antibiotics, salicylates)