Chemical Pathology

Question 1

Bone metabolism and metabolic bone disease
1. Hormones and organs involved in bone metabolism
2. Bone markers
3. Sequence of bone remodelling
4. Define metabolic bone disease
5. Types of metabolic bone disease
Definition
Pathogenesis
Clinical features
Biochemical findings
Treatment

Answer 1

1. Hormones involved in bone metabolism: parathyroid hormone, vitamin D, calcitonin others are estrogen, testosterone, growth hormone, glucocorticoids, thyroid hormone
   Organs involved: kidney, bones and intestine.
   Parathyroid hormone increases calcium reabsorption by stimulating vitamin D. It increases phosphate excretion. It also increases calcium reabsorption in the intestine by active transport which is controlled by vitamin D3.
   Calcitonin secreted in the thyroid glands reduces serum calcium levels by reducing osteoclastic activity. Has no action in the intestine.
   Vitamin D: increases calcium and phosphate reabsorption in the kidneys. It stimulates PTH which increases calcium formation.
2. Bone markers:
   Bone formation markers(specimen: serum): products of osteoblast. Pro peptide of type 1 procollagen, bone ALP, osteocalcin,
   Bone resorption(specimen-serum and urine): products of degradation of type 1 collagen, type 1 procollagen telopeptides, pyridinium cross links
3. Sequence of bone remodeling
   + resting bone with lining cells containing osteocytes
   + lining cells recede and the underlying membrane is removed by metalloproteinase
   + osteoclast are activated and recruited followed by fusion to form multi-nucleated osteoclast.
   + osteoclast digest the underlying bone forming a resorptive cavity
   + osteoblast are recruited to the resorptive cavity
   + osteoblast lay down osteiod which is then calcified
   4 metabolic bone disease can be defined as a group of disease united by a common feature of abnormal chemical milleu characterized by imbalance between bone formation and bone resorption due to abnormalities of minerals and hormones
4. +Osteoporosis and osteopenia
   +osteomalacia and rickets
   +Renal osteodystrophy
   +Paget’s disease
   +bone metastasis

Question 2

Explain the types of mineral bone disease

Answer 2

Osteoporosis/osteopenia: reduction in bone mineral density resulting in weakening of the bone. bone formation is normal while bone resorption is increased. two types; primary (type 1/post-menopausal osteoporosis and type 2/senile osteoporosis) and secondary osteoporosis. all investigations are normal.
osteomalacia; softening of the bone due to defective mineralization due to vitamin D deficiency. ca, phosphate and vitamin D are decreased, PTH and ALP and increased.
Renal osteodystrophy: metabolic bone disease associated with ckd. inability to excrete phosphate. decrease in calcium and vitamin D, Increase in phosphate, PTH and ALP
Paget’s disease: increase osteoblastic and osteoclastic activity. everything is normal except ALP
Bone metastasis: skeletal complication of malignancy. it can have either osteoclastic or osteoblastic character or both. for osteoblastic-prostate cancer, for osteoclastic-multiple myeloma and for both-breast cancer. all are increased.

Question 3

PORPHYRIA
+definition
+classification
+acute porphyria; definition, examples, risk factors, clinical features, laboratory findings and management
+cutaneous porphyria; introduction, examples, skin manifestations, management,
+porphyria cutanea tardia; causes, types, laboratory findings, it is more common in which gender? treatment
+erythropoietic porphyria; explain?? treatment, types
+porphyrinuria; definition, causes

Question 4

CARDIAC MARKERS
+what are cardiac markers?
+importance of cardiac markers
+features of an ideal tumor marker
+current cardiac markers and test panels
+isoenzyme of creatine kinase
+CK-MB- rise and fall of CK-MB
+how to differentiate CK-MB elevation between cardiac and skeletal sources
+troponin; isoenzymes, rise and fall of troponin
+advantages and disadvantage of troponin
+rise and fall of myoglobin
+other markers