laboratory assessment of metabolic disorders

BYPROF. MOUSTAFA RIZK

PROF. OF CLINICAL PATHOLOGYFACULTY OF MEDICINE, UNIVERSITY OF ALEXANDRIA.

Laboratory Assessment Of Metabolic Disorders

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Laboratory assessment of disorders of carbohydrates metabolism

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When food is ingested there is a parallel rise in blood

glucose level. This increase in blood glucose is

sensed by the ß-cells in the pancreas and as a result,

insulin is secreted.

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FROM HYPER TO HYPOGLYC.

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Insulin circulates through the body and signals to

the major insulin sensitive organs: muscle, liver

and fat to increase their glucose intake . Insulin

simultaneously leads to a reduction of glucose

production from the liver and other organs . In this

way the hormone insulin counteracts the rise of

glucose in the blood returning the system to its

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DIABETES MELLITUS

DEFINITION

Diabetes mellitus is a group of metabolic disorders

of carbohydrate metabolism in which glucose is

underutilized, producing hyperglycemia.

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CLASSIFICATION

1.Type 1 DM: autoimmune.

idiopathic.

2. Type 2 DM.

3. Other specific types (2 ry DM):

Acromegaly.

Cortisone treatment.

down’s syndrome

4. Gestational DM.

5. Impaired glucose tolerance.

6. Impaired fasting glucose.10/12/17 06:03

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CRTERIA OF DIAGNOSIS

Type 2 DM. Classical symptoms of diabetes and RBG> 200 mg/dL. OR

FBG ≥ 126 mg/dL. OR

2 hour OGTT ≥ 200 mg/dL.

Gestational DM:

By OGTT: two out of four criteria :

FBG ≥ 105 mg/dL

1 hour ≥ 190 mg/dL.

2 hour ≥ 165 mg/dL.

3 hour ≥ 145 mg/dL.

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Impaired glucose tolerance: Two criteria

FBG < 126 mg/dL

2 h OGTT 140-199 mg/dL.

Impaired fasting glucose: Two criteria

FBG 111-125 mg/dL

2 h OGTT < 140 mg/dL

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ROLE OF THE LAB IN DIABETES MELLITUS

I. Diagnosis: Immunological markers:

-Islet cell antibodies (ICA).

-Insulin auto-antibodies ( IAA).

Genetic markers (e.g., HLA).

Insulin secretion.

Blood glucose.

Oral glucose tolerance curve.

Urine ketones.

Others (e.g., C peptide).

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II. Management:

Acute:

Glucose ( blood- urine)

Ketones (blood-urine)

Acid-base status (PH, bicarbonate).

Lactate.

Other abnormalities related to cellular dehydration or

therapy ( K, Na, phosphate, osmolality)

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Chronic: Glucose (blood-urine)

Glycated proteins(HbA1C-fructosamine)

Urinary protein

Urinary albumin excretion

Proteinuria

Evaluation of complications( renal function, TG, Cholesterol)

Evaluation of pancreas transplant ( C peptide, insulin)

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Laboratory assessment of

disorders of Lipids metabolism

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Major lipids present in plasma:

Fatty Acids Triglycerides Cholesterol Phospholipids

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Triglycerides

Normal level < 160 mg/dl

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Triglyceride Structure

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21Cholesterol

Normal level < 200 mg / dl

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Classification of Lipoproteins

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Lipoprotein metabolism

Exogenous TG Chylomicrons(CM)→ Endogenous TG VLDL→ Exogenous Cholesterol CM→ Endogenous Cholesterol LDL→ Reverse Cholesterol Transport

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Selection of patients for investigations

CHD & vascular disease Family history of coronary disease Risk factors for CHD Clinical features of hyperlipideamia Lipeamic plasma

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Blood sampling for lipid studies

Serum or plasma 12-14 h fasting for TG,HDL & LDL Fasting or no fasting for total cholesterol Usual diet for 2 weeks Avoid vigorous exercise for 1 day

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Serum Cholesterol 140-200 mg/dL Serum Triglycerides: 50-159 mg/dL. HDL-C 35-80 mg/dL

<35 High risk, > 60 Low risk

LDL-C up to 130 mg/dL < 130 Low risk, >160 High risk

HDL/ Total cholesterol >26% Low risk, < 16 % High risk

LDL/HDL > 5% High risk, < 3 % Low risk

Total lipids up to 550 mg/dL.10/12/17 06:03

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LIPOPROTEIN ELECTROPHORESIS

During electrophoresis, the lipoproteins separate (in order of decreasing mobility) into 4 fractions : alpha, pre-beta, beta lipoproteins and chylomicrons

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VALUE OF LIPOGRAM

Increased band                  Patterns

Chylomicrons I

Beta and pre-beta IIb

Broad beta III

Pre-beta IV

Pre-beta and chylomicrons V

Fredrickson DS. Circulation 1975; 51: 209-211.

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Laboratory assessment of some protein disorders

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NORMAL PROTEIN BANDS

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NORMAL PROTEIN BANDS

Albumin 50-60 %α1 Glob 3 - 5 %α2 Glob 5 - 8 %β Glob 8 -12 %Gamma 12-22 %

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PROTEIN DENSITY VERSUS THE CURVE

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INCREASED ALPHA GLOBULINS

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Patterns of Serum Protein Electrophoresis

Alb A1 A2 B GammaChronic N,D N,E E N E infalmmatoryrespnceAcute N,D E E N N,DinflammatoryrespnceSubacuteN,D N E N N

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POLYCLONAL GAMMOPATHY WITH DECREASED ALBUMIN

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INCREASED GAMMA GLOBULINS

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Patterns of Serum Protein Electrophoresis

Alb A1 A2 B GammaHepatic D N N,D bridging cirrhosisMonoclo N,E N,D N N M spikegammopathyMonoclo N,E N,D N M spike N,DgammopathyBiclonal N,E N,D N M spike M spigammopathy

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ACUTE PHASE REACTANTS:

C-reactive protein (CRP). Antiprotease inhibitors. Ceruloplasmin. α1 –acid glycoprotein. Fibrinogen. Haptoglobin. C3.

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Negative acute phase reactants:

Albumin. Transferrin.

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Laboratory assessment of Mineral and bone metabolism

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Minerals important in our body include Minerals important in our body include ::

1- Calcium1- Calcium

2- Phosphorus2- Phosphorus

3- Magnesium3- Magnesium

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11.Parathyroid Hormone:.Parathyroid Hormone:

(A)(A)Synthesis and Secretion :Synthesis and Secretion : PTH is synthesized and secreted by the four PTH is synthesized and secreted by the four

parathyroid glands located on the thyroid parathyroid glands located on the thyroid capsule.capsule.

The conc. of free calcium in blood or extra-The conc. of free calcium in blood or extra-cellular fluid is the primary regulator of PTH cellular fluid is the primary regulator of PTH synthesis and secretion.synthesis and secretion.

Magnesium and 1,25(OH)2 D has a minor Magnesium and 1,25(OH)2 D has a minor influence.influence.

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(B) Biological Action :Biological Action : PTH increases total and free Ca++, decreases

plasma Ph and increases urinary excretion of inorganic Ph.

On bones:- PTH stimulates bone resorption or bone

formation.

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3) In the kidney, PTH : Increases Ca++ reabsorption in the D.C.T. Decreases reabsorption of Ph by proximal T. Inhibits Na+ - H+ antiporter activity which

favors a mild hypercholermic metabolic acidosis in hyperparathyroid states.

Induces 25-hydroxyvit.D – 1α hydrolase, increasing the production of 1,25(OH)2 D which stimulates intestinal absorption of both Calcium and Phosphate.

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(C) Clinical Significance :(C) Clinical Significance :

Determination of PTH is useful : In the D.D. of both hypocalcaemia &

hypercalcaemia. For assessing parathyroid function in renal

failure. For evaluating parathyroid function in bone

and mineral disorders.

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22.Vit. D & its metabolites.Vit. D & its metabolites::

(A)(A) Synthesis :Synthesis : Vit. D is produced endogenously by exposure of

skin to sunlight and is absorbed from food.

It is then metabolized to its main circulatory form, 25-hydroxyvit. D and then to its biologically active form, 1,25(OH)2 D which is the hormone regulating calcium and phosphate metabolism.

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Vit. D & its metabolitesVit. D & its metabolites

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Vit. D & its metabolitesVit. D & its metabolites

(B) Biological Actions of 1,25(OH)(B) Biological Actions of 1,25(OH)2 2 D :D :

Ca and ph. concentrations in serum are maintained by the actions of 1,25(OH)2 D on :

1.intestine.

2.bone.

3. kidney.

4.parathyroid glands.

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Vit. D & its metabolitesVit. D & its metabolites

1) In the Intestine :

1,25(OH)2 D stimulates calcium absorption, by the duodenum & phosphate absorption by the jujenum and ileum.

2) On bone :

1,25(OH)2 D increases bone resorption by stimulating osteaclastic differentiation

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Vit. D & its metabolitesVit. D & its metabolites

3)In the Kidney 3)In the Kidney ::

It inhibits its own synthesis and stimulates its metabolism.

4)On parathyroid glands 4)On parathyroid glands ::

It inhibits the synthesis and secretion of PTH.

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Vit. D & its metabolitesVit. D & its metabolites

(C) Clinical Significance :(C) Clinical Significance :Knowing the concentration of 25(OH)D (which

is the best indication of vit. D nutritional status )because it is:

1.the main circulatory form 2.varies less from day to day with sun exposure &diet 3.easily measuredis useful in evaluating :a) hypocalcaemiab) vit. D statusc) bone diseased) other disorders of mineral metabolism

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3.CalcitoninCalcitonin:

(A) Secretion:

Calcitonin is secreted by the parafollicular or C cells which are distributed throughout the thyroid glands.

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CalcitoninCalcitonin

(B) Biological Actions : Pharmacological doses of calcitonin decrease

serum calcium and ph. concentrations by inhibiting osteoclastic bone resorption.

Multiple forms of Circulating calcitonin have been reported in patients with medullary thyroid carcinomas which occurs as a part of the syndromes of MEN-2A, MEN-2B and familial MTC.

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MARKERS OF BONE METABOLISM

MARKERS OF BONE FORMATION 1-OSTEOCALCIN

2-ALKALINE PHOSPHATASE

3-PROCOLLAGEN PEPTIDES

MARKERS OF BONE RESORPTION

1-COLLAGEN CROSS LINKS

2-TARTARATE RESISTENT ACID P

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MARKERS OF BONE METABOLISM

3-URINARY GALACTOSYL HYDROXYLYSIN

4-URINARY HYDROXYPROLINE

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BONE METABOLIC DISORDERS

OSTEOPOROSIS OSTEOMALACIA PAGETS DISEASE RENAL OSTEODYSTROPHY

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Paget’s disease

Paget’s (pronounced paj-ets) disease affects bones. Throughout a person’s life bone is constantly breaking

down and growing back. With Paget’s disease the normal process of bone growth is changed. The bone breaks down more quickly, and when it grows again it is softer than normal bone.

Soft bones can bend or break more easily. The area affected by Paget’s disease can become shorter because the bone bends.

With Paget’s disease the bone can also grow larger than before.

Paget’s disease can affect any bone, but usually affects the skull, the hip and pelvis bones and bones in the legs and back.

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Lab Studies

Biochemical indices reveal elevated alkaline phosphatase levels of bone origin, due to increased osteoblastic activity and bone formation.

In limited Paget disease, the alkaline phosphatase level may be within the reference range. Procollagen I N-terminal peptide (PINP) recently has emerged as a sensitive serum marker for bone formation.

Many patients with elevated alkaline phosphatase levels have been found to have osteocalcin measurements within the reference range.

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In Paget disease, urinary hydroxyproline levels are elevated as they reflect increased osteoclastic activity and bone resorption.

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THANK YOU PROF./MOUSTAFA RIZK

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