Diabetes Mellitus: Biochemical Aspects — MCQs
Among the following, most reliable test for screening of diabetes mellitus?
Stress hyperglycemia occurs due to all except -
In type I diabetes, which of the following is the MOST characteristic metabolic change that distinguishes it from type II diabetes:-
Mr. Murali has 126 mg/dl of fasting plasma glucose. His venous plasma glucose 2h after ingestion of 75g oral glucose load is 149 mg/dl. This patient comes under which stage of WHO diagnostic criteria of diabetes & intermediate hyperglycemia?
A patient with diabetes mellitus for the past 5 years presents with vomiting and abdominal pain. She is non-compliant with medication and appears dehydrated. Investigations revealed a blood sugar value of 500 mg/dl and the presence of ketone bodies. What is the next best step in management of this patient?
Agent that acts through tyrosine kinase receptor is
Ketone body formation without glycosuria is seen in ?
Glycemic index is defined as:
Obesity has the maximum relative risk for which condition?
A 24-year-old woman presents with recurrent vulvovaginal candidiasis. Which condition should be considered?
Diabetes Mellitus: Biochemical Aspects Indian Medical PG Practice Questions and MCQs
Question 1: Among the following, most reliable test for screening of diabetes mellitus?
- A. Urine sugar
- B. Random sugar
- C. Fasting sugar (Correct Answer)
- D. Glucose tolerance test
Explanation: ***Fasting sugar*** - A **fasting plasma glucose** (FPG) test is the most common and reliable initial test for screening for **diabetes mellitus** because it measures blood glucose after an overnight fast (typically 8-12 hours), providing a baseline level unaffected by recent food intake [1]. - A fasting glucose level of **≥ 126 mg/dL** (7.0 mmol/L) on two separate occasions is diagnostic of diabetes, making it an excellent screening tool for identifying individuals with impaired glucose metabolism [1]. *Random sugar* - A random plasma glucose test can be used to diagnose diabetes if the level is **≥ 200 mg/dL** (11.1 mmol/L) in a symptomatic individual, but it is less reliable for screening asymptomatic individuals due to its variability depending on recent food intake [1]. - Because it can be measured at any time of day without regard to the last meal, it has a **lower sensitivity** for detecting early stages of diabetes compared to fasting glucose. *Glucose tolerance test* - An **oral glucose tolerance test** (OGTT) is highly sensitive and specific for diagnosing diabetes and impaired glucose tolerance, but it is more cumbersome and time-consuming, involving multiple blood draws over two hours after consuming a sugary drink. - While it is a definitive diagnostic test, its complexity makes it **less practical for routine screening** in large populations compared to simpler tests like fasting plasma glucose. *Urine sugar* - The presence of glucose in urine (glycosuria) indicates that blood glucose levels have exceeded the **renal threshold** (typically around 180 mg/dL), meaning the kidneys are unable to reabsorb all the glucose. - This is a **less sensitive and specific** method for screening, as it only becomes positive once blood glucose is significantly elevated, and it does not detect milder forms of impaired glucose metabolism or early diabetes.
Question 2: Stress hyperglycemia occurs due to all except -
- A. Increased level of ACTH
- B. Decreased level of norepinephrine (Correct Answer)
- C. Insulin resistance
- D. Increased level of cortisol
Explanation: ***Decreased level of norepinephrine*** - **Norepinephrine** is a **catecholamine** that generally **increases blood glucose** by stimulating **glycogenolysis** and **gluconeogenesis**. - Therefore, a *decrease* in norepinephrine would *reduce* stress-induced hyperglycemia, making this the exception. *Increased level of ACTH* - **ACTH (Adrenocorticotropic Hormone)** stimulates the adrenal glands to release **cortisol**, which contributes significantly to stress hyperglycemia. - Increased ACTH levels therefore *promote* hyperglycemia in stress. *Insulin resistance* - **Insulin resistance** is a common feature during stress, where target cells become less responsive to insulin's effects. - This reduced insulin sensitivity leads to higher circulating glucose levels, contributing to hyperglycemia. *Increased level of cortisol* - **Cortisol** is a key **stress hormone** that promotes **gluconeogenesis** (production of glucose from non-carbohydrate sources) and **glycogenolysis** (breakdown of glycogen to glucose). - Elevated cortisol levels directly lead to an increase in blood glucose, causing hyperglycemia.
Question 3: In type I diabetes, which of the following is the MOST characteristic metabolic change that distinguishes it from type II diabetes:-
- A. Increased protein catabolism
- B. Decreased glucose uptake
- C. Increased hepatic glucose output
- D. Increased lipolysis (Correct Answer)
Explanation: ***Increased lipolysis*** - In **type 1 diabetes** (T1D), there is an **absolute deficiency of insulin**, which is a potent **anti-lipolytic hormone**. [1] - This lack of insulin leads to unopposed **lipolysis**, resulting in increased free fatty acid (FFA) release, which can be metabolized into **ketone bodies** and contribute to **diabetic ketoacidosis (DKA)**. [2] *Increased protein catabolism* - While protein catabolism is increased in uncontrolled T1D due to the lack of insulin and increased counter-regulatory hormones, it is not the *most characteristic* metabolic change that clearly distinguishes it from type 2 diabetes (T2D), especially in early stages of T2D where some insulin may still be present. [1] - **Protein breakdown** produces amino acids for gluconeogenesis, contributing to hyperglycemia, but **lipolysis leading to ketosis** is more specific to severe insulin deficiency. [3] *Decreased glucose uptake* - **Decreased glucose uptake** by peripheral tissues (especially muscle and adipose tissue) is a characteristic feature of both T1D and T2D. [1] - In T1D, it's due to insulin deficiency, while in T2D, it's primarily caused by **insulin resistance**, making it less specific to distinguish T1D. *Increased hepatic glucose output* - **Increased hepatic glucose output** is a significant contributor to hyperglycemia in both T1D and T2D. [1] - In T1D, it's due to the lack of insulin's suppressive effect on the liver, whereas in T2D, it's due to **hepatic insulin resistance** and increased gluconeogenesis.
Question 4: Mr. Murali has 126 mg/dl of fasting plasma glucose. His venous plasma glucose 2h after ingestion of 75g oral glucose load is 149 mg/dl. This patient comes under which stage of WHO diagnostic criteria of diabetes & intermediate hyperglycemia?
- A. Decreased glucose resistance
- B. IFG - Impaired fasting glucose
- C. Diagnosis of diabetes (Correct Answer)
- D. Impaired glucose tolerance
Explanation: **Diagnosis of diabetes** - The **fasting plasma glucose (FPG)** of 126 mg/dL meets the WHO criterion for **diabetes**, which is FPG ≥ 126 mg/dL [1]. - Although the 2-hour post-glucose load (149 mg/dL) falls within the **impaired glucose tolerance (IGT)** range (140-199 mg/dL), the elevated fasting glucose alone is sufficient for a diabetes diagnosis according to WHO guidelines. *Decreased glucose resistance* - This term is not a standard diagnostic category recognized by the WHO for glucose metabolism disorders. - Glucose resistance is more commonly associated with conditions like **insulin resistance** rather than a specific diagnostic stage [1]. *IFG - Impaired fasting glucose* - **Impaired fasting glucose (IFG)** is defined by a fasting plasma glucose level between 100 mg/dL and 125 mg/dL. - Mr. Murali's fasting glucose of 126 mg/dL is higher than the upper limit for IFG [1]. *Impaired glucose tolerance* - **Impaired glucose tolerance (IGT)** is defined by a 2-hour post-glucose load plasma glucose level between 140 mg/dL and 199 mg/dL. - While Mr. Murali's 2-hour reading of 149 mg/dL falls within this range, the elevated fasting glucose level takes precedence for the overall diagnosis [1].
Question 5: A patient with diabetes mellitus for the past 5 years presents with vomiting and abdominal pain. She is non-compliant with medication and appears dehydrated. Investigations revealed a blood sugar value of 500 mg/dl and the presence of ketone bodies. What is the next best step in management of this patient?
- A. Intravenous fluids
- B. Intravenous insulin
- C. Intravenous fluids with regular insulin (Correct Answer)
- D. Intravenous fluids with long-acting insulin
Explanation: Detailed management of diabetic ketoacidosis (DKA) requires both fluid resuscitation and insulin therapy. ***Intravenous fluids with regular insulin*** - The patient presents with classic signs of **diabetic ketoacidosis (DKA)**: hyperglycemia (blood sugar 500 mg/dl), ketone bodies, dehydration, and a history of diabetes non-compliance [1]. - Initial management for DKA involves aggressive **intravenous fluid resuscitation** to correct dehydration and then **intravenous regular insulin** to lower blood glucose and resolve ketosis [2]. *Intravenous fluids with long-acting insulin* - While fluids are essential, **long-acting insulin** is not appropriate for the acute management of DKA because its slow onset of action makes it inefficient for rapidly correcting hyperglycemia and ketosis. - **Regular insulin** is preferred as it has a quicker onset and shorter duration, allowing for more precise titration in an acute setting [2]. *Intravenous fluids* - Although crucial for correcting **dehydration** and improving renal perfusion, fluids alone will not address the underlying **insulin deficiency** and **ketosis** that define DKA. - Without insulin, the body will continue to produce ketones, exacerbating acidosis [3]. *Intravenous insulin* - Giving intravenous insulin without prior or concomitant **fluid resuscitation** can be dangerous, as it can worsen **hypovolemia** and potentially lead to circulatory collapse by shifting glucose and potassium into cells. - It is critical to first restore **circulating volume** before initiating insulin therapy [2].
Question 6: Agent that acts through tyrosine kinase receptor is
- A. Insulin (Correct Answer)
- B. MSH
- C. TSH
- D. TRH
Explanation: ***Insulin*** - **Insulin** binds to its receptor, which is a **tyrosine kinase receptor**, leading to autophosphorylation and the activation of intracellular signaling pathways. - This activation is crucial for glucose uptake and metabolism by various cells in the body. *MSH* - **Melanocyte-stimulating hormone (MSH)** acts primarily through **G protein-coupled receptors**, specifically melanocortin receptors. - These receptors activate adenylyl cyclase, leading to an increase in intracellular cAMP. *TSH* - **Thyroid-stimulating hormone (TSH)** also acts via a **G protein-coupled receptor** on thyroid follicular cells. - Its binding stimulates adenylyl cyclase, increasing cAMP and thus thyroid hormone synthesis and release. *TRH* - **Thyrotropin-releasing hormone (TRH)** binds to **G protein-coupled receptors** on pituitary thyrotrophs. - This interaction activates the phospholipase C pathway, leading to the release of TSH.
Question 7: Ketone body formation without glycosuria is seen in ?
- A. Diabetes mellitus
- B. Diabetes insipidus
- C. Starvation (Correct Answer)
- D. Obesity
Explanation: ***Starvation*** - During **starvation**, the body depletes its **glycogen stores** and begins to break down **fat for energy**. This process leads to the production of **ketone bodies** (acetoacetate, beta-hydroxybutyrate, and acetone) as an alternative fuel source for the brain and other tissues. - Since there is no underlying problem with **insulin production** or action, blood glucose levels are typically low or normal, and therefore, **glycosuria** (glucose in the urine) is absent. *Diabetes mellitus* - In **uncontrolled diabetes mellitus**, especially Type 1, the body cannot effectively use **glucose** due to lack of insulin, leading to high blood glucose levels (**hyperglycemia**) and subsequently **glycosuria**. - The body then compensates by breaking down **fats**, leading to the formation of **ketone bodies** (**diabetic ketoacidosis**), which results in both **ketonuria** and **glycosuria**. *Diabetes insipidus* - **Diabetes insipidus** is a condition characterized by the inability to conserve water due to insufficient **antidiuretic hormone (ADH)** production or action, leading to excessive urination and thirst. - It does not involve abnormalities in **glucose metabolism** or **ketone body production** and therefore does not typically present with ketonuria or glycosuria. *Obesity* - While **obesity** can lead to **insulin resistance** and is a risk factor for Type 2 Diabetes, it does not directly cause **ketone body formation** in the absence of metabolic derangements such as those seen in uncontrolled diabetes or prolonged starvation. - In most cases of obesity without diabetes, **glucose metabolism** is still adequate enough to prevent significant reliance on **fat breakdown** for energy, meaning there is usually no ketonuria or glycosuria.
Question 8: Glycemic index is defined as:
- A. Glucose control in last 3 months
- B. Measure of the change in the blood glucose following ingestion of proteins
- C. Measure of the change in the blood glucose following ingestion of fats
- D. Measure of the change in blood glucose following the ingestion of carbohydrates. (Correct Answer)
Explanation: ***Measure of the change in blood glucose following the ingestion of carbohydrates.*** - The **glycemic index (GI)** specifically quantifies how much a particular **carbohydrate-containing food** raises blood glucose levels compared to a reference food (pure glucose or white bread). - This value reflects the rate at which **carbohydrates** are digested and absorbed into the bloodstream. *Glucose control in last 3 months* - This description refers to **HbA1c (glycated hemoglobin)**, which provides an average blood glucose level over the preceding 2-3 months. - HbA1c is a clinical measure of long-term glycemic control, not a property of individual foods. *Measure of the change in the blood glucose following ingestion of proteins* - While proteins can affect blood glucose, their impact is generally much smaller and slower compared to carbohydrates, and it's not what the **glycemic index** measures. - The primary role of protein in glucose metabolism is through **gluconeogenesis** or an insulin response, which is distinct from the immediate post-prandial glucose spike from carbohydrates. *Measure of the change in the blood glucose following ingestion of fats.* - Fats have a minimal direct impact on blood glucose levels; they are primarily digested into fatty acids and glycerol. - Although fats can slow down gastric emptying and carbohydrate absorption, they do not directly cause a significant rise in blood glucose and are not considered in the definition of the **glycemic index**.
Question 9: Obesity has the maximum relative risk for which condition?
- A. Cancer
- B. DM (Correct Answer)
- C. Hypertension
- D. CHD
Explanation: ***DM*** - Obesity is a major risk factor for **type 2 diabetes mellitus (DM)**, significantly increasing insulin resistance and pancreatic beta-cell dysfunction. - The relative risk for developing type 2 diabetes attributable to obesity is generally considered to be among the **highest compared to other chronic diseases**. *Cancer* - Obesity is linked to an increased risk of several cancers, including colorectal, breast, and endometrial cancers due to chronic inflammation and hormonal changes. - While significant, the relative risk of obesity for cancer is typically **lower than for type 2 diabetes**. *Hypertension* - Obesity contributes to **hypertension** by activating the sympathetic nervous system and renin-angiotensin-aldosterone system. - Although there is a strong association, the relative risk for hypertension due to obesity is generally **not as high as for type 2 diabetes**. *CHD* - Obesity is a significant risk factor for **coronary heart disease (CHD)** through its association with dyslipidemia, hypertension, and diabetes. - The relative risk for CHD is substantial, but **indirectly mediated** by other comorbid conditions, and the direct relative risk is often surpassed by that of type 2 diabetes.
Question 10: A 24-year-old woman presents with recurrent vulvovaginal candidiasis. Which condition should be considered?
- A. Diabetes mellitus (Correct Answer)
- B. Hypertension
- C. Hypothyroidism
- D. Hyperlipidemia
Explanation: ***Diabetes mellitus*** - **Uncontrolled blood sugar** provides a rich environment for *Candida* overgrowth, leading to recurrent infections [1]. - Impaired immune response in diabetes also makes individuals more susceptible to **opportunistic fungal infections** [1]. *Hypertension* - **Hypertension** is a cardiovascular condition characterized by elevated blood pressure and is not directly linked to fungal infections. - It does not significantly alter the vaginal microenvironment or immune response in a way that would predispose to recurrent candidiasis. *Hypothyroidism* - **Hypothyroidism** involves insufficient thyroid hormone production and can cause symptoms like fatigue and weight gain. - There is no direct physiological link between thyroid hormone levels and susceptibility to vulvovaginal candidiasis. *Hyperlipidemia* - **Hyperlipidemia** is characterized by high levels of lipids (fats) in the blood and is a risk factor for cardiovascular disease. - This condition does not create a predisposition to recurrent *Candida* infections.
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