endocrinology Flashcards
What are the 7 major organs involved in the endocrine system
pituitary gland, thyroid, parathyroid, adrenal glands, pancreas, ovary and testes
What are the properties of water-soluble hormones
transport- unbound
cell interaction- bind to surface receptor
half-life- short
Clearance- fast
Are peptide hormones lipo or hydro-philic
hydrophilic
What are the properties of Fat-soluble hormones
transport- protein bound
cell interaction- diffuse into cell
half life- long
clearance- slow
Are steroid hormones lipo or hydrophilic
lipophilic
what form are peptide hormones in at different stages
Synthesis: preprohormone -> prohormone
Packaging: prohormone -> hormone
Storage: hormone
Secretion: hormone
Are thyroid hormones water soluble
Thyroid hormones are not water soluble, 99% is protein bound.
What is the process of T3 and T4 synthesis and secretion
Tyrosine molecules are incorporated with iodine to form iodothyrosines. These conjugate to give rise to T3 and T4 which are stored in colloid bound to thyroglobulin. T3 and T4 are cleaved from thyroglobulin when TSH stimulates the movement of colloid into secretory cell.
Which hormones have their receptor in the nucleus
oestrogen
thyroid hormone
vitamin D
Which class of hormone has its receptors in the cytoplasm
steriods
What are the features of vitamin D
Fat soluble
Enters cells directly to nucleus to stimulate mRNA production
Transported by vitamin D binding protein
cholesterol derivative
What are the features of adrenocortical and gonadal steroids
95% protein bound
After entering the cell, it passes to nucleus to induce response
Altered to active metabolite
Bind to a cytoplasmic receptor
What are the 5 steps of steroid action
Steroid hormone diffuse through plasma membrane and binds to receptor
Receptor-hormone complex enters nucleus
Receptor-hormone complex binds to GRE
Binding initiates transcription of gene to mRNA
mRNA directs protein synthesis
What are GREs
glucocorticoid-response elements, found in promoter regions of steroid sensitive genes
What is involved in the control of hormone secretion
Basal secretion – continuously or pulsatile
Release inhibiting factors – dopamine inhibiting prolactin, sum of positive and negative effects (GHRH and somatostatin on GH)
Releasing factors
What is involved in the control of hormone action
Hormone metabolism
Hormone receptor induction ( induction of LH receptors by FSH in follicle)
Hormone receptor down regulation
Synergism
Antagonism
What is the hypothalamo-pituitary-thyroid axis
Hypothalamus -> TRH -> anterior pituitary -> TSH -> thyroid gland -> thyroid hormones
What are the 5 functions of thyroid hormone
Accelerates food metabolism
Increases protein synthesis
Enhances fat metabolism
Brain development during foetal life and postnatal development
Growth rate accelerated
What is the endocrine role of the adrenal cortex
Produces steroids hormones:
Mineralocorticoids e.g. aldosterone
Glucocorticoids e.g. cortisol androgens
Androgens e.g. androstenedione and DHEA
What is the endocrine function of the adrenal medulla
Produces epinephrine and norephinephrine
What are the levels of BMI
<18.5 – underweight
18.5-24.9 – normal
25.0-29.9 – overweight
30.0-39.9 – obese
>40 – morbidly obese
How is BMI calculated
weight (kg) / height (m2)
What are 7 major risks of obesity
Type II diabetes
Hypertension
Coronary artery disease
Stroke
Osteoarthritis
Obstructive sleep apnoea
Carcinoma
What 4 carcinomas have an increased risk caused by obesity
Breast
Endometrium
Prostate
Colon
What is the effect of different nutrients on satiety
Highly refined sugar – quick and short satiety
Low glycaemic index foods – better
High protein – prolonged satiety
High fat – stimulate and entice people to eat more
Which region of the brain plays a central role in appetite regulation
Hypothalamus
What is the structure and action of peptide YY
36 amino acids
Structurally similar to NPY
Binds NPY receptors
Secreted by neuroendocrine cells in ileum, pancreas and colon in response to food
Inhibits gastric motility
Reduces appetite
what is NPY
Neuropeptide Y
It stimulates food intake, preferably carbohydrates
What is Cholecystokinin’s effect on appetite regulation
Receptors in pyloric sphincter
Delays gastric emptying
Gall bladder contraction
Insulin release
And via vagus – satiety
What 4 stimuli are involved in increasing appetite
Olfactory, gustatory, cognitive and visual stimuli
Which hormone stimulates food intake
Ghrelin
What is the role of stretch receptors in the stomach
increase satiety
What 4 hormones increase satiety
CCK, Glucagon like peptide-1 (GLP), insulin and Peptide YY
Define Diabetes Mellitus
A disease in which the body’s ability to produce or respond to the insulin is impaired, resulting in abnormal metabolism of carbohydrates and elevated levels of glucose in the blood.
Name 6 types of diabetes
Type 1
Type 2 – includes gestational and medication induced diabetes
Maturity-onset diabetes of the young (MODY)
Pancreatic diabetes
Endocrine diabetes – Cushing’s/ acromegaly
Malnutrition related diabetes
What is the pathology of diabetes
Chronic hyperglycaemia due to insulin dysfunction – can’t move glucose from blood into cells. Leads to low glucose in cells with starve of energy.
Define type 1 diabetes
an insulin deficiency disease characterised by loss of beta cells due to autoimmune destruction.
Define type 2 diabetes
inappropriately low insulin secretion and peripheral insulin resistance
What is the disease process of diabetes
Lack of insulin drives the mobilisation of energy stores from muscles, fat and the liver
Glucose accumulates in the blood, causing hyperglycaemia
In the kidneys, the glucose reabsorption mechanism becomes saturated and glucose appears in the urine
Glucose within renal tubules draws water in by osmosis, leading to osmotic diuresis
The raised plasma osmolality stimulates the thirst centre
Over time, diabetes damages capillaries and markedly accelerates atherosclerosis
how does acromegaly cause secondary diabetes
excessive secretion of growth hormone. Insulin resistance rises.
How does cushing’s syndrome cause secondary diabetes
increased insulin resistance, reduced glucose uptake into peripheral tissues.
What is the process of drug-induced diabetes
glucocorticoids increase insulin resistance
What causes type 1 diabetes
initiated by genetic susceptibility and environmental triggers
What causes type 2 diabetes
combination of genetic predisposition and environmental factors (obesity and lack of physical activity)
What causes MODY
single gene defect altering beta cell function
What are 6 subacute clinical presentations of diabetes
Thirst (osmotic activation of hypothalamus)
Polyuria (osmotic diuresis)
Weight loss and fatigue (lipid muscle loss due to unrestrained gluconeogenesis)
Hunger (lack of useable energy source)
Pruritis vulvae and balanitis
Blurred vision (due to uptake of glucose/ water into lens)
What are 5 suggestive features of type 1 Diabetes
Onset in childhood/ adolescence
Lean body habitus
Acute onset of osmotic symptoms
Prone to ketoacidosis
High levels of islet autoantibodies
What are 3 suggestive features of type 2 diabetes
Usually presents in over 30s
Onset is gradual
Diet, exercise and oral medication can often control hyperglycaemia
What are 4 suggestive features of MODY
Parents affected with diabetes
Absence of islet autoantibodies
Evidence of non-insulin dependence
Sensitive to sulphonyl urea
What are 3 investigations for diabetes
Fasting >7mmol/L plasma glucose
Random plasma glucose >11mmol/L
HbA1c 6.5%/ 48mmol/mol
What are 3 methods of neuropathy screening for diabetes
sensation (10mg monofilament), vibration perception (tuning fork), ankle reflexes.
What are the consequences of missing a type 1 diabetes diagnosis
It can lead to fat metabolism and the formation of ketone bodies.
What is the process of ketone body production in type 1 diabetes
reduced insulin leads to fat breakdown, forming free fatty acids, which:
Impair glucose uptake
Are transported to the liver, providing energy for gluconeogenesis
Are oxidised to form ketone bodies (acetone, beta-hydroxybutyrate)
Ketone bodies dissolve in the blood and release H+, causing acidosis.
What is the process of Ketoacidosis
Absence of insulin and rising counterregulatory hormones leads to increasing hyperglycaemia and rising ketones.
Glucose and ketones escape in the urine but lead to an osmotic diuresis and falling circulating blood volume
Ketones cause anorexia and vomiting
What is Diabetic Ketoacidosis (DKA) characterised by
hyperglycaemia, raised plasma ketones and metabolic acidosis
What are 4 symptoms of DKA
Polyuria and polydipsia
Nausea and vomiting
Weight loss
Abdominal pain
what are 6 signs of DKA
Hyperventilation
Dehydration
‘Fruity breath’
Hypotension
Tachycardia
Coma
What are the 4 steps in management of DKA
Rehydration
Insulin
Replacement of electrolytes (K+)
Treat underlying cause
What are 6 complications of diabetes
Leading cause of blindness in working age adults – diabetic retinopathy
Diabetic nephropathy – leading cause of end-stage renal disease
Peripheral vascular disease
Stroke
Cardiovascular disease – leading cause of mortality
Diabetic Peripheral Neuropathy – leading cause of non-traumatic lower extremity amputations
what are 4 ways that diabetes causes morbidity and mortality
Acute hyperglycaemia- metabolic emergencies, DKA, HHS
Hyperglycaemic hyperosmolar state
Chronic hyperglycemia- tissue complications
side effects of treatment- hypoglycemia
What are 4 features of Diabetic neuropathy
Pain – burning, paraesthesia
Autonomic – orthostatic hypotension, constipation, ED
Insensitivity – foot ulceration, Charcot foot, amputation
Peripheral neuropathy – glove and stocking sensory loss
What are 4 risk factors for diabetic neuropathy
hypertension, smoking, changes in HbA1c, diabetes duration
What are 3 treatment methods for diabetic neuropathy
good glycaemic control, anticonvulsants, opioids.
What are 3 features of diabetic retinopathy
Micro-aneurysms: pericyte and smooth muscle loss
Leakage: basement membrane thickening reduced junctional contact with endothelial cells
Ischaemia: pericyte loss
What is the treatment of diabetic retinopathy
laser therapy to stabilise changes, not improve sight.
What is the core aim to management of type 1 diabetes
Restore the physiology of the beta cell
What are the methods to management of type 1 diabetes
Insulin treatment (twice daily with meals)
Awareness of blood glucose lowering effect of exercise
Ability to judge CHO intake
DAFNE: dose adjustment for normal eating (reduces DKA and severe hypos)
What is the first line treatment for Type 2 diabetes
Weight loss and exercise are substantial and will reverse hyperglycaemia
What is the issue with the first line treatment for type 2 diabetes
Patients with type 2 diabetes don’t tend to respond to these lifestyle changes, due to their lifestyle choices.
What is the second line treatment for type 2 diabetes
Medication to control BP, blood glucose and lipids.
Metformin = weight loss
Metformin + sulphonyl urea but side effect of weight gain + chance of hypo
Insulin
What is Hyperglycaemic Hyperosmolar state (HHS) and who does it affect
A complication of diabetes mellitus in which high blood sugar results in high osmolarity without significant ketoacidosis.
unwell patients with type 2 DM
What are 6 symptoms of HHS
Weakness
Leg cramps
Vision problems
An altered level of consciousness
marked dehydration
glucose >30mmol/L.
What is the effect on ketonemia in HHS
There is no switch to ketone metabolism, so ketonemia stays <3MMOL/L AND PH >7.3.
What is the typical osmolality in HHS
> 320mosmol/kg.
What are the dangers of occlusive events in HHS
focal CNS signs, chorea, Disseminated intravascular coagulation (DIC), leg ischaemia
What is the management of HHS
Give LMWH prophylaxis to all unless contraindication
Rehydrate slowly with 0.9% saline IVI over 48h
Replace K+ when urine starts to flow
what are the 3 mechanisms for increased levels of thyroid hormone
Overproduction of thyroid hormone
Leakage of preformed hormone from thyroid
Ingestion of excess thyroid hormone
What are 5 causes of Hyperthyroidism
Grave’s disease
Toxic multinodular goitre
Toxic adenoma
Congenital hyperthyroidism
Thyroiditis
What are 7 symptoms of hyperthyroidism
Weight loss
Tachycardia
Anxiety
Heat intolerance
Sweating
Diarrhoea
Menstrual disturbance
What are 3 specific signs to graves’ disease
Diffuse goitre
Thyroid eye disease
Acropachy
What is the specific sign for adenomal hyperthyroidism
Solitary nodule
What is euthyroid hyperthyroxinemia
Euthyroid hyperthyroxinemia is defined as a condition in which the serum total T4 and T3 concentrations are increased, but the thyroid-stimulating hormone (TSH) concentration is normal and there are no clinical signs or symptoms of thyroid dysfunction.
What are 3 investigations for thyroid diseases
Thyroid function tests to confirm biochemical hyperthyroidism
Clinical history, physical signs usually sufficient for diagnosis
Supporting investigations – thyroid antibodies
What are 4 treatments for hyperthyroidism
Antithyroid drugs e.g. thionamides (carbimazole)
Beta blockers
Radioiodine
Surgery (partial/ subtotal thyroidectomy)
Define Graves’ disease
An autoimmune disease affecting the thyroid that causes hyperthyroidism and results in an enlarged thyroid.
What is the pathology of graves disease
The immune system is tricked into targeting receptors on the thyroid gland, causing it to become overactive - hyperthyroidism.
Increased levels of TSH receptor stimulating antibody (TRAb) which causes excess thyroid hormone secretion (low TSH in the blood stream, but high thyroid hormone levels (T3 and T4) due to the TRAb having the same effects as TSH on the thyroid).
What are 7 symptoms and signs of graves disease
Anxiety and irritability
A fine tremor of your hands or finger
Heat sensitivity and an increase in perspiration or warm, moist skin
Weight loss, despite normal eating habits
Enlargement of thyroid gland (goiter)
Bulging eyes – Graves’ ophthalmopathy
Thick, red skin usually on the shins or tops of the feet - Graves’ dermopathy
What is the core aim of management of graves disease
Inhibition of the production of thyroid hormones and to block the effect of the hormones on the body.
What are 5 methods involved in the management of graves disease
Radioactive iodine therapy – oral radioactive iodine. This destroys the overactive thyroid cells over time, causing the gland to shrink and to lessen symptoms gradually
Anti-thyroid medications – interfere with the thyroid’s use of iodine to produce hormones e.g. carbimazole
Beta blockers e.g. propranolol – provide rapid relief of irregular heartbeats, tremors, heat intolerance and muscle weakness
Ophthalmopathy – corticosteroids/ orbital decompression surgery
Thyroidectomy
Define primary Hypothyroidism
Subnormal activity of the thyroid gland due to intrinsic underactivity of the thyroid gland.
Define secondary hypothyroidism
Subnormal activity of the thyroid gland due to reduced stimulation of the gland caused by a deficiency of TSH due to disease of the pituitary gland
define tertiary hypothyroidism
Subnormal activity of thyroidgland due to low TRH caused by hypothalamic disease
What is the most common type of hypothyroidism, its proportion of all cases and is most common cause
Primary
>99%
Most cases due to Hashimoto’s thyroiditis (autoimmune hypothyroidism)
What are the 3 main causes of Adult primary hypothyroidism
Hashimoto’s thyroiditis
Thyroidectomy
Iodine deficiency
What is the main cause of adult secondary hypothyroidism
Pituitary tumour
What are the 3 main causes of child hypothyroidism
Neonatal hypothyroidism
Resistance to thyroid hormone
Isolated TSH deficiency
What are 14 symptoms of hypothyroidism
Fatigue, loss of energy, lethargy
Weight gain
Decreased appetite
Cold intolerance
Dry skin
Muscle pain, joint pain, weakness in the extremities
Depression
Emotional lability, mental impairment
Forgetfulness, impaired memory, inability to concentrate
Constipation
Menstrual disturbances, impaired fertility
Decreased perspiration
Paraesthesia and nerve entrapment syndromes
Blurred vision
What are 10 signs of hypothyroidism
Weight gain
Slowed speech and movements
Dry skin
Jaundice
Pallor
Coarse, brittle, straw-like hair
Loss of scalp hair, axillary hair, pubic hair, or a combination
Hoarseness
Bradycardia
Pericardial effusion
What are the differential diagnoses to hypothyroidism
Addison disease
Goiter
Chronic fatigue syndrome
Hypopituitarism
Iodine deficiency
What are the investigations for hypothyroidism
Sinus bradycardia, low pulse pressure, pericardial effusion, coronary artery disease
TSH and thyroxine tests
What are the outcomes of TSH and T3/T4 tests for primary hypothyroidism
Increased TSH, usually decreased free T4, decreased T3
T4/T3 may be below normal in positive titre of TPO antibodies in Hashimoto’s