Endocrinology Flashcards
What is the definition of diabetes mellitus?
Impaired production or response to insulin, resulting in raised blood glucose levels.
What are the classifications of diabetes?
Type 1, type 2, gestational, other specific types (e.g. MODY).
Is T1D insulin dependent or independent?
Insulin dependent.
What are the symptoms of T1D?
Polydipsia, polyuria, weight loss and fatigue.
What are the long term complications of diabetes (T1D and T2D)?
Macrovascular: coronary artery disease, peripheral artery disease, stroke, hypertension.
Microvascular: retinopathy, nephropathy, neuropathy, diabetic foot.
Infections: UTIs, pneumonia, skin & soft tissue, fungal.
Insulin secretion is dependent on what?
Glucose uptake by GLUT2 receptors, which stimulates insulin release from beta cells.
What are the actions of insulin?
Insulin binds to its receptor causing movement of GLUT4 receptors to the cell surface, stimulating glucose uptake into the cell.
Insulin causes decreased hepatic production of glucose (gluconeogensis and glycogenolysis).
Insulin also causes increased peripheral glucose uptake (glucose transport, glycogenesis).
What is the common presentation of T2D?
Asymptomatic detected on routine testing.
Or polydipsia, polyuria and complications e.g. infected foot.
What are normal blood glucose levels in a non diabetic?
Before meals: 4.0-5.9 mmol/L
90 mins after meals: < 7.8 mmol/L
What are target blood glucose levels in a type 1 diabetic?
Before meals: 4.0-7.0 mmol/L
90 mins after meals: 5.0-9.0 mmol/L
What are the target blood glucose levels in a type 2 diabetic?
Before meals: 4.0-7.0 mmol/L
90 mins after meals: < 8.5 mmol/L
What are normal, prediabetes and diabetes HbA1c levels?
Normal: < 42 mmol/mol
Prediabetes: 42-47 mmol/mol
Diabetes: 48 mmol/mol or greater
What is the role of insulin and where is it produced?
Insulin causes uptake of glucose into cells for energy and causes muscle and liver cells to uptake glucose from the blood and store it as glycogen (glycogenesis). Insulin also inhibits glycogenolysis, gluconeogenesis and lipolysis. It is produced from the beta cells of the pancreatic islets of langerhans in response to high blood glucose levels.
What is the role of glucagon and where is it produced?
Glucagon causes the liver to break down glycogen into glucose (glycogenolysis). It also stimulates gluconeogensis (production of glucose from fats and proteins) in the liver. Glucagon is produced by the alpha cells of the pancreatic islets of langerhans in response to low blood glucose levels and stress.
What is ketogenesis?
Ketogenesis occurs when there is insufficient glucose supply in cells and glycogen stores are exhausted. The liver converts fatty acids into ketones. Ketones are water soluble so can cross the BBB and used by the brain for energy. Ketones are normally buffered so the blood doesn’t become acidotic, but in patients with T1D with extreme hyperglycaemic ketosis it results in metabolic acidosis (diabetic ketoacidosis).
What is T1D?
Autoimmune destruction of beta cells in pancreatic islets of langerhans resulting in insulin deficiency and hyperglycaemia.
What is the typical onset of T1D?
Children and adolescents.
Which viruses are linked to T1D development?
Coxsackie B virus and enterovirus.
Which auto-Abs are involved in T1D pathophysiology?
Anti-GAD and islet cell Abs (ICA).
Which HLA genes are linked to T1D?
HLA-DR3 and HLA-DR4.
What causes weight loss in T1D?
Fluid loss and muscle/fat breakdown.
Which tests would you do for suspected T1D?
Random blood glucose level, urine dipstick, laboratory glucose, HbA1c, auto-Abs screen, C-peptide.
Describe the different types of insulin regimes
Basal bolus: long acting insulin in evening and short acting insulin 3x per day 30 mins before meals.
1, 2 or 3 injections per day: mix of both short and intermediate acting insulin (70/30).
Insulin pump: injects short acting insulin through a cannula inserted under the skin.
Why should patients cycle their injection sites of insulin?
Because lipodystrophy can occur which prevents absorption of insulin.
How is diabetes monitored?
HbA1c measured every 3-6 months.
Capillary blood glucose 4 times per day (one before each meal and one before bed).
Flash glucose monitoring (libre) measures glucose of interstitial fluid.
Diabetic review - injection site, retinopathy, nephropathy, diabetic foot, CV risk factors, thyroid disease.
What are the acute complications of T1D?
Hypoglycaemia and DKA.
What causes hypoglycaemia in diabetic patients?
Secondary to insulin or suphonylureas, not enough carbohydrates or not processing carbohydrates properly (D+V).
What are the symptoms of hypoglycaemia?
Hunger, tremor, sweating, palpitations, anxiety, irritability, dizziness and pallor.
Serious (< 2.8 mmol/L) - decreased consciousness, seizures, coma and death.
How would you manage hypoglycaemia?
Oral: rapid acting glucose (e.g. lucozade) and slower acting carbohydrates (e.g. biscuits/toast).
Severe cases: IV dextrose and IM glucagon.
What are the precipitating factors for DKA?
First presentation of T1D, poor diabetic control (not taking insulin), intercurrent illness e.g. infection.
What are the 3 features of DKA?
Hyperglycaemia (> 11 mmol/L).
Ketonaemia (> 3 mmol/L).
Acidosis (HCO3- < 15 mmol/L or venous pH < 7.3).
What is the pathophysiology of DKA?
Lack of insulin leads to hyperglycaemia. This is exacerbated by glycogenolysis, gluconeogensis and increased hormone secretion (cortisol, glucagon and GH). Lipolysis occurs leading to free FA, which are then converted into ketones. Build up of ketones in the blood causes acidosis. Excess glucose is filtered into the urine, causing osmotic diuretics, leading to polyuria and dehydration. As insulin normally drives potassium into the cell, there is high serum potassium but low total body potassium. Treatment with insulin can lead to hypokalaemia and arrhythmias.
What are the symptoms and signs of DKA?
Polydipsia, polyuria, N+V, acetone smell to breath, dehydration, hypotension, altered consciousness, abdominal pain and kussmaul breathing.
How would you manage DKA?
IV fluids, insulin infusion, glucose monitoring, potassium monitoring, treat infections, fluid balance chart and ketone monitoring.
When should HbA1c be used with caution?
Conditions interrupting erythropoiesis (e.g. EPO use, iron deficiency), haemoglobinopathies, glycation (e.g. CKD, alcoholism), red cell survival (e.g. haemolysis, splenectomy).
Is HbA1c appropriate for diagnosis of diabetes in children/young people?
No - also not appropriate in pregnancy.
What is the role of incretins?
Incretins are hormones produced by the GI tract. They’re secreted in response to large meals and act to decreased blood glucose. They increase insulin secretions, inhibit glucagon production and slow absorption by GI tract. GLP-1 is an incretin. DPP-4 is an enzyme that inhibits incretins.
What are the risk factors for T2D?
Non-modifiable: age, ethnicity (black, Chinese, south Asian), FHx/genetics, low birth weight, PCOS, Hx of GDM.
Modifiable: obesity, sedentary lifestyle, high carbohydrate diet, medications (e.g. corticosteroids).
What is the pathophysiology of T2D?
Insulin resistance: related exposure to glucose and insulin —> cells become insulin resistant —> more insulin is required to produce an effect —> failed glucose uptake —> chronic hyperglycaemia.
Insulin deficiency: high glucose levels toxic to beta cells —> beta cell depletion and pancreatic fatigue —> decrease insulin secretion.
What is involved in the oral glucose tolerance test (OGTT)?
Baseline fasting plasma glucose measured prior to breakfast in the morning. Then give 75g glucose drink and measure plasma glucose 2 hours later.
What is the diagnostic criteria for pre-diabetes?
HbA1c: 42-47 mmol/mol.
Impaired fasting glucose - fasting glucose: 6.1-6.9 mmol/L.
Impaired glucose tolerance - plasma glucose at 2 hours: 7.8-11.1 mmol/L.
What is the management for pre-diabetes?
Education and lifestyle changes - no medication. Potentially reversible with weight loss and exercise.
What is the diagnostic criteria for T2D?
HbA1c: > 48 mmol/mol.
Random glucose: > 11 mmol/L.
Fasting glucose: > 7 mmol/L.
OGTT: > 11 mmol/L.
What is the management for T2D?
Education and lifestyle changes —> low glycaemic, high fibre diet, exercise, weight loss, stop smoking, decrease alcohol intake, manage other diseases (e.g. hypertension, hyperlipidaemia, CVD).
Monitor for complications.
Monitor HbA1c and blood glucose levels.
Medication: 1st line (metformin), 2nd line (metformin + sulfonylurea/pioglitazone/DPP-4 inhibitor/SGLT-2 inhibitor), 3rd line (metformin + 2 drugs above OR metformin + insulin).
What are the acute complications of T2D?
Hypoglycaemia and hyperosmolar hyperglycaemic state (HHS).
What are the characteristics of HHS?
Hypovolaemia, hyperglycaemia, absent ketonaemia, high osmolarity.
What is the pathophysiology for HHS?
Relative insulin deficiency and elevated counter-regulatory hormones (e.g. cortisol, glucagon, GH) —> reduced glucose utilisation, increased gluconeogensis, increased glycogenolysis —> hyperglycaemia —> osmotic diuresis.
What are the symptoms of HHS?
Polydipsia, polyuria, N+V, muscle cramps, weakness, altered mental state, seizures, coma.
What is the management of HHS?
Fluid resuscitation, IV insulin infusion, electrolyte replacement, cardiac monitoring.
What are the complications of HHS?
MI, thrombotic events (hyperosmolar state —> hyperviscosity of blood), cerebral oedema.
Describe the role of bariatric surgery in the management of T2D
Bariatric surgery among T2D patients improves micro- and macrovascular complications. Post-operative weight loss and better glycaemic control. Effects on tissue-specific insulin sensitivity, beta cell function and incretin responses. Remission of diabetes in some patients.
What is metabolic syndrome?
Combination of diabetes, hypertension and obesity.
How would you treat diabetic nephropathy?
ARB/ACEi, SGLT2 inhibitor, statins.
Hypertension and glycaemic control.
What is the general treatment for diabetic foot ulcers?
Offloading, control of foot infection, control of ischaemia, wound debridement and wound dressings.
What is the relationship between mental health problems/eating disorders and T1D?
Diabetic patients can develop an unhealthy relationship or fixation with food because their disease is linked to diet, weight and body image. E.g. skipping insulin to lose weight, binge eating to make themselves vomit, food restriction, or over-exercising. Up to 30% of patients with T1D have an eating disorder.
What was the outcome of the diabetic control and complications trial (DCCT) on glycaemic control targets and progression of T1D complications?
The study showed that patients with T1D who keep their blood glucose levels as close to normal as safely possible with intensive diabetes treatment as early as possible in their disease have fewer diabetic complications compared to those on conventional treatment.
Why is carbohydrate counting important in T1D?
It means that insulin dose can be individually matched to your carbohydrate intake, leading to better glycaemic control.
Why is there increased CVD risk in T1D?
Accelerated atherosclerosis from inflammation.
How would you manage CV risk in patients with T1D?
Insulin, statins, BP control, aspirin and lifestyle changes.
Describe the role of transplant interventions in the management of T1D
Pancreatic islets cell transplant - beta cell replacement therapy. Available on NHS on a specific criteria.
Short-acting insulin is also known as…
Regular or soluble insulin.
Long-acting insulin mimics what type of insulin secretion?
Background secretion.
What is the insulin to carbohydrate ratio?
For every 10g carbohydrate you need 1 unit of insulin.
What are the pharmacological and surgical interventions for obesity?
Drugs - orlistat and liraglutide.
Bariatric surgery.
Why is HbA1c not recommended as a diagnostic test for patients with suspected T1D?
Because it may not reflect a recent rapid rise in blood glucose and results take longer than with serum glucose testing.
What is the relationship between obesity and the development of T2D?
Adipose tissue releases pro-inflammatory cytokines leading to insulin resistance. Increased waist circumference is associated with increased risk of developing T2D.
Describe tiered services in obesity management
Tier 1 - behavioural.
Tier 2 - lifestyle, diet, nutrition.
Tier 3 - MDT approach, weight management clinics, medical management.
Tier 4 - bariatric surgery.
What is the classification of obesity (BMI)?
Class 1: 30-34.9
Class 2: 35-39.9
Class 3: 40+
How would manage obesity?
Education, very low calorie diet, exercise programme, orlistat, liraglutide, bariatric surgery.
How does orlistat reduce weight in obesity?
Inhibits GI lipase, impairing absorption.
What is the role of leptin?
Suppresses appetite, secreted by adipose tissue.
What is the role of ghrelin?
Stimulates appetite, secreted by stomach.
Which hormones are released by the anterior pituitary?
TSH, ACTH, FSH, LH, GH and prolactin.
Which hormones are produced by the posterior pituitary?
Oxytocin and ADH.
Describe the thyroid axis
Hypothalamus releases TRH, which stimulates anterior pituitary to release TSH, which stimulates thyroid to released T3 and T4. T3 and T4 negatively feedback on TRH and TSH.
Describe the adrenal axis
Hypothalamus releases CRH, which stimulates anterior pituitary to release ACTH, which stimulates the adrenal cortex to release cortisol. Cortisol negatively feedbacks suppressing release of CRH and ACTH.
What is the role of cortisol in the body? When is it secreted?
Inhibits immune system, inhibits bone formation, raises blood glucose, increases metabolism and increases alertness (stress hormone).
Diurnal variation —> cortisol peaks early in morning and lowest in the late evening.
Describe the growth hormone axis
GHRH released by hypothalamus, stimulates GH to be released from anterior pituitary, which stimulates release of IGF-1 from liver. IGF-1 stimulates bone growth, muscle growth and cell regeneration and reproduction. Somatostatin inhibits GH secretion.
Describe the parathyroid axis
PTH released from parathyroid glands in response to low serum calcium, low magnesium and high serum phosphate. PTH increases serum calcium via increasing osteoclast activity causing reabsorption of calcium from bone into blood. PTH also increases calcium reabsorption in kidneys. PTH stimulates activation of vitamin D in kidneys which promotes calcium absorption in small intestine. High serum calcium suppresses PTH release (negative feedback) to reduce serum calcium level.
Describe RAAS system
Renin secreted by juxtaglomerular cells in afferent arterioles in kidneys in response to low BP. Renin converts angiotensinogen (released by liver) into angiotensin 1. ACE (released by lungs) converts angiotensin 1 into angiotensin 2. Angiotensin 2 causes vasoconstriction, increases sympathetic activation and increases ADH secretion. Angiotensin 2 also stimulates aldosterone release from adrenal gland. Aldosterone increases sodium reabsorption and in turn water reabsorption (and increases potassium secretion). This all acts to increase BP.
What are the functions of thyroid hormones?
Stimulate metabolic rate, positive inotropic and chronotropic effects on heart, involved in growth and development.
Which is the active thyroid hormone?
T3.
Conversion of T4 —> T3 in muscle, liver, kidney and brain.
Which hormone is used to screen for thyroid disease?
TSH.
If TSH is abnormal then T3 and T4 are measured.
Describe TFT results for primary hyperthyroidism
TSH: low
T3 & T4: high
Describe TFT results for secondary hyperthyroidism
TSH: high
T3 & T4: high
Describe TFT results for subclinical hyperthyroidism
TSH: low
T3 & T4: normal
Describe TFT results for primary hypothyroidism
TSH: high
T3 & T4: low
Describe TFT results for secondary hypothyroidism
TSH: low
T3 & T4: low
Describe TFT results for subclinical hypothyroidism
TSH: high
T3 & T4: normal
Anti-TPO Abs are present in which diseases?
Grave’s disease and Hashimoto’s thyroiditis.
Anti-thyroglobulin Abs are present in which diseases?
Grave’s disease, Hashimoto’s thyroiditis and thyroid cancer.