Diabetes mellitus definition,classification,clinical features ,investigation
DEFINATION, CLASSIFICATION ,CLINICAL FEATURES AND
FARRUKH MASOOD ,NMC
• Diabetes is a group of metabolic diseases characterized by hyperglycemia resulting
from defects in insulin secretion, insulin action, or both. The chronic hyperglycemia
of diabetes is associated with long-term damage, dysfunction, and failure of different
organs, especially the eyes, kidneys, nerves, heart, and blood vessels.
(American Diabetes Association)
According to WHO Diabetes is if
Fasting Glucose =>7mmol or 126mg/dl
Random Glucose =>11.1mmol or 200mg/dl
• Human Insulin is a 51 amino acid dimeric protein composed of alpha
and beta chains held together by disulphide bond.
• It is produced as a preproinsulin molecule by ribosomes, matures to
proinsulin molecule in golgi apparatus and cleaves to insulin and Cpeptide chain before its packing into secretory granules.
CLASSIFICATION OF DIABETES
• Type 1 Diabetes (IDDM)
• Type 2 Diabetes(NIDDM)
• Gestational Diabetes
• Other specific types
TYPE 1 DIABETES MELLITUS(IDDM)
It occurs mostly in young group of patients <30 years.
Insulin deficiency results due to destruction of beta cells
T cell mediated autoimmune destruction of beta cells /glutamic acid decarboxylase antibodies (GAD Abs)
Genetic predisposition (HLA- DR3 DR4 genes)
30-50% concordance in identical twins
• Environmental factors (viruses, excessive coffee intake, stress, cow milk in newborn )
It is usually associated with thyroid disease, Addison disease ,Pernicious anemia, Coelic disease.
TYPE 2 DIABETES MELLITUS (NIDDM)
• It mostly affects middle age and older people (>30 years)
• It occurs due to Insulin resistance and beta cell exhaustion (relative insulin deficiency)
• High insulin levels in the early stage is characteristic.
• Central obesity ( ↑FFA compete with glucose for oxidation ,adipokines decreases sensitivity of insulin receptors ,inhibits
Metabolic syndrome (obesity, hypertension,↑LDL,↑TAGs,etc)
Genetic predisposition (TCFL2 gene)
BMI >30 kg/m2
MATURE ONSET DM (MODY)
A type of type 2 DM occurring in young people
It is further divided into
MODY 1 (HNF 4a deficiency)
MODY 2 (glucokinase deficiency)
MODY 3 (HNF 1a deficiency)
MODY 4 (IPF-1 deficiency)
MODY 5 HNF-1b deficiency)
• It is the hyperglycemia occurring for the first time during pregnancy
• Placental hormones reduce the sensitivity of insulin receptors
resulting in hyperglycemia and insulin doesn’t meet body requirement
and beta cell exhaustion occurs
OTHER SPECIFIC TYPES
Genetic defects of beta cells
Genetic defects of insulin action e.g lipodystrophy
Pancreatic disease (pancreatitis,cystic fibrosis,neoplasm,hemochromatosis)
Drug induced DM (steroids,thiazides,diuretics)
Viral (congenital rubella,mumps, coxasackie )
Uncommon form of immune mediated DM
Endocrine Induced DM (thyrotoxicosis,Cushing
• Testing the urine for glucose with dipsticks is a common practice for detecting diabetes.
• Preferably it should be checked after 2 hrs of meal for its maximum sensitivity
• It may be false positive in pregnancy and with some drugs
• Ketonuria can also be detected in the urine by dipsticks
• To check for ketone bodies in urine ,nitroprusside reaction is used
• Ketonuria may aslo be false positive in case of prolonged strenuous exercise ,vomiting, dehydration but if with
glycosuria diabetes is most likely diagnosis
• Standard dipstick testing for albumin detects urinary albumin at concentration >300mg/dl.
• Microalbuminuria in the absence of UTI is an indicator of diabetes.
Normal fasting blood glucose =<7mmol or 126mg/dl
Normal random blood glucose =<11.1mmol or 200mg/dl
FBG = ≥126mg/dl
RBG = ≥200mg/dl
• Oral Glucose Tolerance Test (also called the OGTT) : The OGTT is a two-hour test that checks
your blood glucose levels before and 2 hours after you drink a special sweet drink. It tells the
doctor how your body processes glucose. Diabetes is diagnosed at 2 hour blood glucose of greater
than or equal to 200 mg/dl
• Before people develop type 2 diabetes, they almost always have "prediabetes" — blood glucose levels that are
higher than normal but not yet high enough to be diagnosed as diabetes.
• Doctors sometimes refer to prediabetes as impaired glucose tolerance (IGT) or impaired fasting glucose (IFG),
depending on what test was used when it was detected. This condition puts you at a higher risk for developing
type 2 diabetes and cardiovascular disease.
Results indicating prediabetes are:
An A1C of 5.7% – 6.4%
Fasting blood glucose of 100 – 125 mg/dl
An OGTT 2 hour blood glucose of 140 mg/dl – 199 mg/dl
• Glycated hemoglobin provides an accurate and objective measure of
glycemic control over a period of 2-3 months
• In diabetes ,the slow non enzymatic covalent attachment of glucose to
hemoglobin increases the amount of Hb1ac relative to HbA
• To be diabetic, Hb1ac should be ≥6.5%
• Renal function tests should be evaluated as creatinine may
• Electrolyte balance should be evaluated in case of diabetic