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The term secondary diabetes mellitus is used when hyperglycemia develops secondary to some other known disease and treatment of the primary disease alleviates hyperglycemia. The cause of secondary diabetes mellitus are as follows:-
1) Pancreatic diseases
2) Endocrine disorders .
3) Drugs & Chemical induced
4) Genetic syndromes
5) Associated with cancers
6) Liver diseases
7) Chronic renal failure
 Pregnancy
9) C.N.S disorders
10) Insulin receptor abnormalities
11) Stress induced
1) Pancreatic diseases
eg. - Acute pancreatitis/Chronic pancreatitis,
- Chronic fibrocalculous pancreatitis
- Cancer of pancreas specially tail region.
All of these conditions can manifest with hyperglycemia.
In acute pancreatitis - Reduced Insulin release with increased glucocorticoids, glucagon and catecholamine levels occur.
In chronic pancreatitis - Steatorrhoea, pancreatic calcification and diabetes mellitus are the chief manifestations.
Cancer pancreas:- If it involves tail region then diabetes mellitus may manifest with venous thrombosis, migratory thrombophlebitis, G.I. haemorrhage and splenomegaly. After 90% removal of pancreas
hyperglycemia occurs.
2) Endocrine disorders : Effect of hormones on carbohydrate metabolism
a) Adrenaline & Noradrenaline: These hormones increase and release FFA and this
leads to peripheral insulin resistance. Glycogenolysis is increased and also inhibit
insulin secretion.
b) Growth Hormone Increases insulin resistance.
c) Corticosteroids: Increases glycogenolysis.
d) Thyroxin: Increases gut motility and absorption of glucose. Hence hyperthyroidism is
associated with impaired glucose tolerance.
In acromegaly overt D.M. is seen in 20% cases and manifests with only insulin resistance. In 20-40% show abnormal glucose tolerance.
Cushing's Syndrome Cushing's Disease:- Impaired G.T.T is common in this group. Elevated serum glucose leads to increased glycolysis and increase in peripheral insulin resistance. Those who have familiar predisposition become overt diabetics. (20%)
Schmidt's syndrome:- This is an association of diabetes mellitus with primary Addison's disease.
Hyperthroidism: Mild post prandial hyperglycemia occurs in hyperthyroidism due to increase in gut motility which leads to increased glucose absorption. In hypothyroidism or hyperthyroidism of autoimmune thyroiditis as underlying cause, patient may show antibodies against Islet cell and develops diabetes mellitus.
Pheochrocytoiua: 50% show impaired G.T.T. in pheochromocytoma. This is due to increased hepatic glycogenolysis and reduced insulin release from beta cells due to raised catecholamines.
Liver disorders & hyperglycemia
Hemochromatosis or bronze D.M. patient presents with arthropathy, hepatomegaly, skin pigmentation, hypogonadism and congestive cardiac failure. Pancreas is damaged due to iron deposition (65%) and marked insulin resistance is a feature.
Stress induced hyperglycemia.: Myocardial infarction, cerebral haemorrhage and .severe burns are associated with increased catecholamine levels iri blood. This in turn causes reduced insulin secretion and produces peripheral insulin resistance.
Genetic syndromes
Werner s syndrome and lipodystrophy, pineal hypertrophy syndrome, and ataxia telengectasia are associated with impaired G.T.T.
Drugs & Chemicals
Steroids, thiazides, dilantin, nifedipine, diazoxide, can produce impaired G.T.T. or overt D.M. in genetically predisposed persons.
Cancer & D.M.
Chronic malnutrition and steroid therapy can cause hyperglycemia. Certain cancers are common in diabetes like pancreatic carcinoma, endometrial carcinoma and gall bladder carcinoma.
Azotemic pseudodiabetes: Chronic renal failure causes raised post prandial blood sugar due to hypokalemia and decrease insulin action and peripheral insulin resistance.
Hyper Ureceniia: Uric acid is structurally similar to Alloxan. Gout, is at times associated with diabetes mellitus.
Gestational DM.: D.M. occurring during pregnancy is called gestational diabetes. Diabetic status disappears with delivery, 5-10% may later become permanently diabetic. Pregnancy is associated with many anti-insulin like hormones like human placental lactogen(H.P.L), growth hormone, oestrogen, progesterone, and cortisol All these cause impaired G.T.T.
Conclusion
There are many clinical situations where hyperglycemia occurs transiently. Treatment of primary pathology or removal of offending agent if done then diabetic status gets completely reversed.
REFERENCES
1. Diabetes mellitus- Daniel W. Foster, page 1980 in Harriason's Principles of Internal
Medicine Vol. 213th Edition Me Graw Hill Incorporation, New York, 1992.
2. Etiology of Diabetes- Stephen Podolsky- in clinical Diabetes Modern Management
1981 Apple ton-Century-Crafts/New York.
3. Report of WHO study on Diabetes Mellitus-1985. Technical report series 727 WHO
Geneva.
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Pregnancy