Vitamins

1. Vit D – functions and disorders will be
continued on 30/11/2023
9 to 11:15am
 For seminar on 30/11, 01/12, 02/12
 Topic Vitamin D- active co-enzyme
forms, functions, RDA, dietary sources,
deficiency manifestations, toxicity IS
CHANGED TO
 Vitamin D- synthesis & activation,
mechanism of action, RDA & dietary
1

2. Case reports to be written in
Biochemistry Practical Records,
to be submitted on 30 November,
1st and 2nd December
2

3. Case Report on Vit K & Vit D-
18/11/2023
A preterm neonate of 34 weeks gestational age was
observed to have bleeding for a longer time at the site
of phlebotomy after the withdrawal of blood for routine
investigations. The prothrombin time was found to be
prolonged but the platelet count was normal.
1) Which vitamin deficiency causes the above
symptom?
Vitamin K deficiency
2) What is the RDA of the above vitamin?
RDA = 50 – 100 µg/day or 1 µg/kg/day
3

4. 3. List the biochemical functions of the above vitamin.
Vitamin K is necessary for coagulation.
It acts as a cofactor for the gamma-carboxylation of
glutamic acid residues of clotting factors II, VII, IX and
X.
This is a part of the post translational modification of
the clotting factors which are synthesized in the liver as
inactive zymogens.
Vitamin K dependent gamma carboxylation is also
required for functional activity of osteocalcin (protein
synthesized by osteoblasts which binds to
hydroxyapatite crystals of the bone promoting
mineralization), Bone Gla protein, Matrix Gla protein,
4

5. A 3 yr old child was brought to the OPD by his mother with
complaints of deformity in the lower limbs and failure of eruption of
teeth. On examination, it was found that the anterior fontanellae had
not yet closed, teeth had not yet erupted; swellings were present at
the costochondral junction with a deformed chest. Widening of the
wrist and bowed legs were also seen.
 Investigations: Serum Calcium: 7.75 mg/dl (9-11mg/dl), Serum
Phosphorus: 3.5 mg/dl (2.5-4.5mg/dl), Serum Alkaline
Phosphatase (Bone Isoenzyme): 450 IU/L (50-150IU/L), X-ray
findings confirmed the findings of bowed legs and deformed
chest.
1) What is the diagnosis?
2) Which vitamin deficiency causes the above symptoms?
3) How is the vitamin converted to its biologically active form in the
body?
4) What is the role of the above vitamin in Calcium and Phosphorus
metabolism? 5

6. A 3 yr old child was brought to the OPD by his mother with
complaints of deformity in the lower limbs and failure of eruption of
teeth. On examination, it was found that the anterior fontanellae had
not yet closed, teeth had not yet erupted; swellings were present at
the costochondral junction with a deformed chest. Widening of the
wrist and bowed legs were also seen.
 Investigations: Serum Calcium: 7.75 mg/dl (9-11mg/dl), Serum
Phosphorus: 3.5 mg/dl (2.5-4.5mg/dl), Serum Alkaline
Phosphatase (Bone Isoenzyme): 450 IU/L (50-150IU/L), X-ray
findings confirmed the findings of bowed legs and deformed
chest.
1) What is the diagnosis?
Nutritional Deficiency Rickets
2) Which vitamin deficiency causes the above symptoms?
Vitamin D Deficiency
6

7. 3. How is the vitamin converted to its biologically active form in the
body?
7

8. 4. What is the role of the above vitamin in Calcium and Phosphorus
metabolism?
Calcitriol increases serum calcium and phosphorus levels. It has the
following actions:
a) on the intestinal epithelial cells- calcitriol increases absorption of
dietary calcium and phosphorus, by increasing production of and
stimulating all proteins and enzymes required for Ca & P
absorption
b) on the renal tubular epithelial cells to increase reabsorption of
calcium and phosphorus thus preventing loss of calcium and
phosphorus in urine
c) On the bone, when serum calcium is normal or high, calcitriol
acts on osteoblasts, osteoclasts and osteocytes promoting bone
remodelling, mineralization and increasing bone mineral
density. When serum calcium levels are low- there will be PTH
secretion. PTH & Calcitriol stimulate osteoclasts that lead to
bone demineralization and normalization of serum Calcium8