Abstract
Background:
Metformin, which is a biguanide is administered in patients with Type 2 Diabetes Mellitus, mainly works on by decreasing the synthesis & subsequent production of glucose in the liver via attenuating the hepatic gluconeogenesis. As Type 2 DM is characterized by insulin resistance & this insulin also inhibits production of sex hormone binding globulin (SHBG) in the liver resulting in increased concentrations of free testosteron, researches done worldwide, showed that metformin therapy improves insulin sensitivity, leading to reduced serum insulin and androgen levels. It was also shown that metformin treatment has additional beneficial effects on metabolic profile and clinical manifestations of hyperandrogenism. But researches done in eastern Indian population is scarce.

Aim:
With this background, we conducted this study with the following objective - to study the difference in serum insulin & SHBG level between recently diagnosed Type 2 DM patients not taking any anti diabetic medication and age and gender matched diagnosed diabetic patients taking metformin for at least 3 months .

MMethods:
It is a cross sectional, descriptive, non interventional, hospital based study that took place in Medical College & Hospital, Kolkata over the period of 4 months (Jan 24 – April 24). Known diagnosed diabetic patients taking metformin for at least 3 months who will come to central laboratory, MCH, Kolkata, after going through the inclusion exclusion criteria were included as one arm of the study. And also suspected diabetic patients getting diagnosed for the first time and not taking any anti diabetic medication were included as another arm after going through the inclusion exclusion criteria. Proper informed cosent was obtained from each patient. SHBG estimation is done in ADVIA CENTAUR chemiluminiscence assay, it is sandwich immunoassay. Insulin is also measured in ADVIA CENTAUR chemiluminiscence assay.

Results:
As per our study, both recently diagnosed male & female patients of type 2 DM ( n= 50) had high serum insulin levels (39.7 +- 2.3 micro IU/ml ) than age and gender matched diagnosed type 2 DM patients ( n= 50) who took metformin for at least 3 months (26.2 +- 1.5 micro IU/ml) ( p value < 0.005) , and this change is significant, proving metformin is a possible factor behind decreased circulating insulin level.And our study also showed that , recently diagnosed male patients of type 2 DM ( n = 27 ) had less amount of SHBG (29.2 +- 3.1 ng/ml) than diagnosed male type 2 diabetic patients (taking metformin for at least 3 months) ( n = 27 out of 50 ) (53.6 +- 4.5 ng/ml) ( p value < 0.005). Same goes for female patients, there recently diagnosed type 2 diabetic patients (without taking metformin) (n= 23 out of 50 ) had less SHBG level (34.7 +- 6.1 ng/ml) than diagnosed female type 2 diabetic patients (taking metformin for at least 3 months) ( n = 23 out of 50 ) ( SHBG level - 92.6 +- 3.5 ng/ml) ( p value < 0.005).

Conclusion:
The limitation of our study was small sample size and cross sectional pattern of the study. Bigger sample size & prospective cohort type study designing method could be a better method to predict and assess before after values of Insulin & SHBG after treatment with a specific dosage of metformin.

Key words: Insulin, SHBG (Sex hormone binding globulin), Metformin