Endocrinology Flashcards
What is a hormone?
endogenous, signalling molecule released from endocrine gland travelling in the blood and binding to target cells causing a change/response
What is the other term for the neurohypophysis?
Posterior pituitary
What is the other term for the adenohypophysis?
Anterior pituitary
What neurones originate in the SON and PVN of the hypothalamus and project into the posterior pituitary?
Magnocellular neurones
What hormones are stored in the posterior pituitary gland?
OT and AVP
Outline the blood supply to the anterior and posterior pituitary gland.
Superior hypophyseal artery supplies entering primary capillary plexus then hypophyseal portal veins of infundibulum and then to the secondary plexus of hypophyseal portal system Inferior hypophyseal artery supplies posterior pituitary gland by entering capillary plexus of infundibular process and leaves by posterior hypophyseal veins
What is the venous drainage of the pituitary gland?
Posterior hypophyseal vein drains posterior pituitary
Anterior hypophyseal vein drains anterior pituitary
Where is the pituitary gland located?
3/4cm directly between middle of the eyebrows in sphenoid bone fossa called sella turcica
Outline the MOA of ADH in dehydration.
Dehydration —> plasma osmolarity increases —> osmoreceptors in hypothalamus (circumventricular organs) fire —> ADH released —> retain water by absorption at the collecting duct of the nephron in kidney —> homeostatic
What hormones are released from the anterior pituitary gland?
Mnemonic: FLAT PeG
FSH
LH
ACTH
TSH
PL
GH
What is a tropic hormone?
Give an example of a pituitary hormone that is a tropic hormone.
stimulates another gland to produce its hormone
FSH
LH
ACTH
TSH
What two anterior pituitary cell types exist?
How may these be detected?
Eosin staining in histology
Acidophilic (pink cytoplasm):
- Sommatotrophs
- Lactotrophs
Basophilic (purple cytoplasm):
- Corticotrophs
- Thyrotrophs
- Gonadotrophs
Mnemonic: PeG is Pink
Prolactin
GH
What is unique about somatomammotrophs?
degree of plasticity and under differing physiological conditions can be converted to allow production of more than one type of hormone
What is the MOA of Tolvaptan?
V2 receptor non-selective antagonist binding at V2r in kidney
What tubular protein allows retrograde movement of AQP2 vesicles towards the apical membrane along actin filaments?
Dynein
Which type of cells produced GH?
Somatotrophs in the anterior pituitary gland
What gene polymorphism can increase your risk of T1DM?
DR4-DQ8
Where is Insulin produced?
ß-cells of Islets of Langerhans in Pancreas
Outline the process of Ketogenesis.
Prolonged starvation with insufficient intracellular glucose, leading to exhaustion of glycogen stores which then results in ketogenesis involving lipolysis and conversion to ketones.
Three ketones:
- Acetoacetate
- ß-HB
- Acetone
What is the clinical presentation of T1DM?
- Polyuria (b/c osmotic diuresis > tubular reabsorption)
- Polydipsia (fluid and electrolyte losses 2º to polyuria)
- Weight loss (fluid depletion and muscle atrophy 2º insulin deficiency)
- Fatigue
- Candida infection
- Young individual
- Blurred vision
- Nausea/ vomiting (DKA)
- Abdominal pain (DKA)
- Tachypnoea (DKA)
- Coma/ Unresponsive (DKA)
What investigations would you order in a suspected case of T1DM and what would you expect to see?
- Random Plasma Glucose (RPG): ≥ 11mmol/L
- Oral Glucose Tolerance Test (OGTT): ≥11mol/L
- Fasting Plasma Glucose (FPG): ≥7mmol/L
- Serum/urine ketones: Present
- HbA1c: ≥48mmol/L (≥6.5%)
- Autoimmune markers: Positive
- C peptide (low)
To be positive in T1DM, what value threshold should be exceeded in a RPG?
> 11mmol/L
To be positive in T1DM, what value threshold should be exceeded in a FPG?
> 7mmol/L
To be positive in T1DM, what value threshold should be exceeded in a OGTT?
> 11mmol/L
What is the long-term management of T1DM?
- Conservative: Physical activity/ Diet (low sugar, high in low GI carbs, sweeteners, protein)/ 3 meals/ Notify DVLA
+ - Insulin (Basal-bolus or CSII): insulin glargine (SC OD)/ insulin isophane (SC BD)/ insulin detemir (SC BD)/ insulin degludec (SC OD) + insulin lispro/ insulin aspart
When calculating insulin doses, how much energy is related to units of insulin?
1U insulin = 10g carbs
What drug may be given should postprandial hyperglycaemia persist?
Pramlintide
Outline how Pramlintide works?
Amylin is co-secreted with insulin to reduce postpradial glucose by: increases gastric emptying time, reduces appetite (anorexia) and reduces postprandial glucagon secretion
Give an example of a rapid-acting insulin.
Insulin Lispro
Insulin Aspart
What type of insulin is Isophane insulin?
Intermediate
Give an example of a long-acting insulin.
Insulin Glargine
Insulin degludex
Insulin Detemir
How is Insulin Glargine made?
Glycine substituted for Asparagine (N-terminal) and 2 arginine AAs added to end of beta chain thus ∆ isoelectric point = less soluble thus dissolve slowly
How is insulin degludec made?
Conjugation to FA (hexadecanedioic acid) -> hexamer formation
How is Insulin Detemir made?
FA (myristic acid) conjugated to lysine -> albumin binding = slowly dissociates
Give some side effects of insulin.
Oedema;
Lipodystrophy
Hypoglycaemia
Give 5 RFs of T2DM.
- Ageing
- Physical inactivity
- Overweight/Adiposity
- Hypertension
- Dyslipidaemia
- FHx
Outline the pathophysiology involved in T2DM.
- Reduced insulin sensitivity: pre-receptor (Abs/secretion defects)/receptor (volume/ affinity)/ post-receptor (IRS-1/PI3K/AKT/GLUT4) -> reduced uptake of glucose = hyperglycaemia -> increased conversion to lipid (WAT) = adiposity -> reduced HDL/ increased TGs/ increased LDL; accumulation of AGEPs/free radicals -> chronic inflammation -> macroscopic + microscopic complications of diabetes
What are the clinical features of T2DM?
- Fatigue
- Blurred vision
- Recurrent candida infection: vaginal/ penile/ skin folds
- Skin infection: cellulitis/abscesses
- UTI: Cystitis/ Pyelonephritis
What are the glucose thresholds for the following investigations:
- FPG
- RPG
- OGTT
- HbA1c
- HbA1c: ≥ 48mmol/L (6.5%)
- FPG: ≥ 7mmol/L
- RPG: ≥ 11mmol/L
- OGTT: ≥ 11mmol/L
What is the long-term management of a patient with T2DM?
- Conservative: diet/ physical activity/ sweeteners/ weight loss/ smoking cessation
+ - Biguanide: Metformin
± - Antihypertensives: Lisinopril/Enalapril/ Amlodipine/ Diltiazem
+ - Lipid control: Atorvastatin/ Rosuvastatin/ Simvastatin/ Pravastatin
+ - Antiplatelets: Aspirin/ Clopidogrel
HbA1c above goal on metformin
- Metformin
+
- Hypoglycaemic drug: SGLT2i/ GLPi/ DPP4i/ Sulfonylurea/ Basal insulin
What is the MOA of Metformin?
Enters via OCT-1 and acts on Mt to increase AMP:ATP ratio. Activation of AMPK increases glucose transport, FA oxidation, reduces lipogenesis and reduces glycogenolysis
What are the side effects of Metformin?
Appetite suppression
Weight gain
Diarrhoea
Give an example of a Sulfonylurea.
Gliclazide
Tolbutamide
Glibenclamide
What is the MOA of the sulfonylureas?
Block ATP-sensitive K+ channels in ß-cells which causes ß-cell depolarisation and increased insulin secretion
What are the side effects of Gliclazide?
Nausea
Diarrhoea
Hypoglycaemia
Abdominal pain
Give an example of a GLP-1 analogue.
Exenatide
Liraglutide
What is the MOA of Exenatide?
Give the class of Exenatide.
Mimic GLP-1 binding at A-cells and ß-cells to cause insulin release and reduce glucagon
What side effects would you warn a patient about regarding commencing Exenatide?
Reduced appetite
Nausea/Vomiting
Diarrhoea
GI disorder/discomfort
Dizziness
Skin reactions
Pancreatitis
Which anti-diabetic medication may cause Pancreatitis?
GLP-1 Analogues such as Exenatide/Liraglutide
DPP4-i such as Sitagliptin
Give an example of a drug that is a DPP4-inhibitor?
Sitagliptin
Linagliptin
What class of drug is Sitagliptin?
DPP4-i
What class of drug is Sitagliptin?
DPP4-i
What is the MOA of Sitagliptin?
Inhibit DPP4 thus enhance endogenous incretin effects to increase insulin and decrease glucagon
A patient is about to commence drug trial on Sitagliptin. What side effects should you warn them about?
Headache
Pancreatitis
Hypersensitivity
What class of drug is Empagliflozin?
SGLT2 inhibitor
What is the MOA of Cangliflozin?
Inhibit Na+-Glucose transporters in PT and LoH thus giving glycosuria
A patient is about to commence drug treatment on Empagliflozin. What side effects would you warn them about?
Hypoglycaemia
Hypovolaemia
Skin reaction
UTI
Urosepsis
Balanoposthitis
Constipation
What class of drug is Pioglitazone?
Thiazolidnediones (TZD)
What is the MOA of Glitzone?
What class is it?
Thiazolidinedione (TZD)
PPARy agonist thus increases transcription of insulin signalling
What side effects would you warn a patient commencing Glitazone?
They ask you what class this drug is, what do you say?
Risk of infection
Visual impairment
Weight gain
Bone fracture
What anti-diabetic medication may increase the risk of bone fracture?
Thiazolidinediones (TZDs) such as Pioglitazone which suppress bone formation
What class of drug is acarbose?
Alpha-glucosidase inhibitor
Give an example of an alpha-glucosidase inhibitor.
Acarbose
What is the MOA of acarbose?
Alpha-glucosidase inhibitor which results in reduced carbohydrate absorption.
What are the common side effects of alpha-glucosidase inhibitors such as Acarbose?
Flatulence
Diarrhoea
Outline the pathophysiology of a DKA.
Reduced insulin production causing hyperglycaemia which results in osmotic diuresis causing polyuria and polydipsia whilst starvation state leads to lipolysis and ketogenesis with ketoacidosis resulting in metabolic acidosis and abdominal pain due to gastroparesis
What are the clinical features of DKA?
- Nausea/ vomiting
- Pear smelling breath
- Reduced consciousness: Reduced mental status
- Abdominal pain: peritonitis (guarding)/ early bowel obstruction (tinkling bowel sounds)/ late bowel obstruction (absent bowel sounds)
- Hyperventilation: Kussmaul breathing
What breathing pattern may be noted in DKA?
Why does it happen?
Deep, rapid breathing pattern as respiratory compensation to blow of CO2 to counteract metabolic acidosis
What investigations may be suggestive of a DKA?
- Blood glucose: ≥ 11.0mmol/L
- VBG: Metabolic acidosis (raised anion gap, reduced bicarbonate); pH ≤ 7.40
- Blood ketones: Ketonaemia (≥ 3.0mmol/L)
- U+E: Raised SCr and hyperkalaemia
How would you manage a patient with DKA?
- Insulin: 0.1units/kg/hr
- IV Fluids: NaCl (0.9%) at 1L in 30 minutes, 1L over 1hr, 1L over 2hr, 1L over 4hr
± (Hypokalaemia)
- IV Fluids: KCl added (1L for 2hr, 1L for 2hr, 1L for 4hr, 1L for 4hr, 1L for 6 hr)
- -> 10mmol/L KCl if [K+] = 3-5mmol/L; 20mmol/L KCl if [K+] = ≤3.5mmol/L
± (Glucose ≤ 14mmol/L)
- IV Glucose: Glucose (10%)
Describe a Hyperosmolar Hyperglyaecimic State?
Profound hyperglycaemia (≥ 30mmol/L) and hyperosmolality (≥ 320mOsm/kg) and volume depletion in the absence of ketoacidosis – a complication of diabetes.
What are the osmolality and blood glucose thresholds for HHS?
- Blood glucose: ≥30mmol/L
- Serum osmolality: ≥ 320mOsm/kg
How do you manage a Hyperosmolar Hyperglycaemic State?
- Insulin: 0.05units/kg/hr \+ - IV Fluids: NaCl (0.9%) at 1L in 30 minutes, 1L over 1hr, 1L over 2hr, 1L over 4hr \+ - IV Fluids: KCl added (1L for 2hr, 1L for 2hr, 1L for 4hr, 1L for 4hr, 1L for 6 hr) \+ ± (Glucose ≤ 14mmol/L) - IV Glucose: Glucose (10%)
A patient asks you what the complications of Diabetes Mellitus are. Outline what you may tell them.
Infection: Hyperglycaemia reduces function of leucocytes which increases risk of infection: cellulitis, boils, abscesses, candidiasis.
Skin disease: Diabetes produces a myriad of common dermatological manifestations
Iatrogenic hypoglycaemia: Increased usage of insulin results in hypoglycaemia.
Lactic Acidosis: Rare complication when taking Metformin presenting with severe metabolic acidosis without hyperglycaemia or ketosis. Treat by rehydrating and infusing bicarbonate (1.26%)
Retinopathy (background/proliferative): Damage to the vessels supplying the retina (central retinal artery) seen as haemorrhage, oedema, microaneurysms and exudate (HOME).
Nephropathy: Damage to vessels (ischaemic lesion) or urinary tract (infective lesion, UTI) or glomerular basement membrane (glomerulopathy) leading to compromised filtration (renal insufficiency) demonstrated by proteinuria, Hypercreatinemia and hypoalbuminemia.
Erectile Dysfunction (ED): Damage to vasculature of penis (pudendal artery)/ cavernosal artery leading to inability for corpus cavernosum to remain filled in erect state. Manage with PDEi (sildenafil) and counselling.
Diabetic Foot: Potential damage due to neuropathy which results in tissue necrosis, similar to PAD: pale, pulseless, painless, absence of hair, shiny skin. Diabetic foot ulcers may be seen
Macrovascular complications: Diabetes is a risk factor for atherosclerosis which is summative with other risk factors (hypertension/hyperlipidaemia/obesity/ low physical inactivity) resulting in damage to large vessels which is territory-dependent – PAD (peripheral), CVA (brain) and MI (heart).
What types of Diabetic Neuropathy exist?
Symmetrical sensory neuropathy: reduced sense of vibration, pain sensation and temperature
Diabetic amyotrophy: painful wasting which is asymmetrical in the quadriceps causing loss of bulk and diminished reflexes
Acute Painful neuropathy: Neuropathic pain with paraesthesia dn dysesthesia
Mononeuritis (/Multiplex): Inflammation of nerves with sudden onset and pain common at sites of external pressure (e.g. Carpal Tunnel Syndrome)
Autonomic neuropathy: affects ANS causing CVS and GI and urinary and sexual Sx and S
What is the most common form of pituitary disease?
Pituitary adenoma
How may a pituitary adenoma present?
Headache
Visual changes: Reduced visual acuity; Bitemporal hemianopia; Diplopia
Hypogonadism Sx: infertility; reduced libido; hot flushes
Prolactinoma: gynaecomastia; galactorrhoea; reduced libido; amenorrhoea/oligomenorrhoea
Acromegaly: coarsened facial features; joint pain; soft tissue hypertrophy; galactorrhea; erectile dysfunction
Cushing’s Disease: Mood change; Striae; Facial plethora; Amenorrhoea; Weight gain; OP; Acne; Reduced libido
What is the first-line, gold standard investigation used to diagnose a Pituitary Ademona?
MRI-Pituitary to delineate characteristics of tumour including invasion and compression of surrounding structures
How do you manage a Pituitary Adenoma?
Microadenoma:
- Observation
Macroadenoma: Abutting or Not Abutting Optic Chiasm
- Trans-sphenoidal surgery
+
- Hormone replacement (FLAT PeG): Testosterone; Estradiol; Progesterone; Hydrocortisone; Levothyroxine; Somatropin
± Mass Effect
- Radiotherapy: Stereotactic gamma knife
± (Residual tumour if surgery + radiotherapy fails)
- Octreotide
How may pituitary adenomas be classified?
Non-Functional: No hyper secretion of hormone
‘Clinically Non-Functioning Pituitary Adenoma’ (CNFPA)
Functional: Hyper-secretion of hormone
Microadenoma <1cm
Macroadenoma >1cm
Functional (hormone type):
- Prolactinoma
- Somatrotroph adenoma
- Gonadotroph adenoma
Pituitary apoplexy: associated with neurological deficit or symptomatic (haemorrhage/infarction) with few/no symptoms
The rapid enlargement of a pituitary tumour due to infarction or haemorrhage causing severe headache and sudden, severe vision loss is termed?
Pituitary Apoplexy
In hypopituitarism, radiographic imaging of via MRI-Pituitary showing an empty space is termed?
Empty sella syndrome
A deficiency of GnRH in a patient with anosmia is termed?
Kallmann’s Syndrome
Pituitary infarction following severe postpartum haemorrhage is termed?
Sheehan’s Syndrome
What is the aetiology of Hypopituitarism?
VITAMIN-C
Vascular: Pituitary apoplexy; Sheehan’s Syndrome; Carotid artery aneurysms
Infective: Basal meningitis; Encephalitis; Syphilis
Infiltrations: Haemochromatosis; Sarcoidosis
Trauma: Skull Fx; Surgery
Acquired: Drugs
M
Immunological: Pituitary antibodies
Neoplasia: Primary tumour; Secondary tumour; Lymphoma
What investigations would you conduct in a suspected Hypopituitarism?
FBC
Hormones
MRI-Pituitary
How do you manage hypopituitarism?
HRT: Hydrocortisone; Levothyroxine; Testosterone; Estriol; Somatropin
What is the most common cause of Hyperprolactinaemia?
Give other causes.
Prolactinoma (functional pituitary adenoma)
Pituitary adenoma which compresses pituitary stalk to disinhibit DA which suppresses PL (disconnection)
Primary hypothyroidism
Drugs (D2 antagonists)
Acromegaly/PCOS (co-secretion)
What effect does thyroid have on prolactin?
High TSH levels in hypothyroidism can stimulate prolactin
What is the criteria for a macroadenoma?
> 10mm
How do you manage Hyperprolactinaemia?
Conservative: Withdraw offending drugs \+ Medical: Cabergoline; Bromocriptine \+ Surgery: Transphenoidal approach
± Macroadenoma pressing optic chaise
- Radiotherapy
What is the difference between acromegaly and gigantism?
Excessive GH production in children prior to growth plate closure results in gigantism
Excessive GH production in adults once epiphyseal plates are closed results in acromegaly
What is the main cause of acromegaly?
Somatotroph adenoma (functional GH-secreting pituitary adenoma)
What are the clinical features of acromegaly?
Changes n facial appearance
Headaches
Visual deterioration
Deep voice
Galactorrhoea; Impotence; Poor libido
Tiredness; Weight gain; Diaphoresis; Musculoskeletal pain
Prognathism
Interdental separation
Large tongue
Hirsutism
Spade-like hands and feet
Tight rings
CTS
Arthropathy Glycosuria Hypertension Heart failure Oedema
What is the management of Acromegaly?
Medial: Octreotide; Cabergoline
+
Surgical: Trans-sphenoidal surgical resection
± Incomplete surgical excision
External radiotherapy
Explain the difference between Cushing’s Disease and Cushing Syndrome.
Cushing disease is a condition caused by ectopic cortisol production in pituitary adenoma or ectopic ACTH production from adrenal adenoma
Cushing Syndrome is the myriad of symptoms associated with elevated cortisol