Endocrinology Flashcards
(131 cards)
Adrenocortical axis
Hypothalamus I CRH I Anterior Pituitary I ACTH I Adrenal gland I Cortisol
Primary adrenal insufficiency
Pathophysiology and examples
- Adrenal glands themselves are damaged, resulting in a reduction in secretion of cortisol and aldosterone
- Most common cause is autoimmune
- Example: Addisons
Secondary adrenal insufficiency
Pathophysiology and examples
- Result of inadequate ACTH stimulating the adrenal glands, resulting in low cortisol release
- Due to loss or damage of the pituitary gland
- Examples: pituitary surgical removal, infection, loss of blood flow, radiotherapy
- Sheehan’s syndrome: massive blood loss during childbirth leads to pituitary gland necrosis
Tertiary adrenal insufficiency
Pathophysiology and examples
- Result of inadequate CRH release by the hypothalamus
- Usually the result of long term oral steroids (>3 weeks) causing suppression of hypothalamus
- When exogenous steroids are suddenly withdrawn, the hypothalamus does not ‘wake up’ fast enough and endogenous steroids are not adequately produced
What is released by the anterior pituitary gland?
- Thyroid stimulating hormone (TSH)
- Adrenocorticotropic hormone (ACTH)
- Follicle stimulating hormone (FSH) and luteinising hormone (LH)
- Growth hormone (GH)
- Prolactin
What is released by the posterior pituitary gland?
- Oxytocin
- Antidiuretic hormone (ADH)
Diabetes
What is secreted by alpha cells
Glucagon
Diabetes
What is secreted by beta cells
Insulin
Diabetes
What is secreted by D-cells
Somatostatin
Diabetes
What is secreted by PP/F cells
Pancreatic polypeptides
Where are alpha- and beta- cells?
Islets of Langerhans in the pancreas
Basic pathology of T1DM
Autoimmune disorder where the insulin-producing beta cells of the islets of Langerhans in the pancreas are destroyed by the immune system
This results in an absolute deficiency of insulin resulting in raised glucose levels
Patients tend to develop T1DM in childhood/early adult life and typically present unwell, possibly in diabetic ketoacidosis
Basic pathology of T2DM
This is the most common cause of diabetes in the developed world. It is caused by a relative deficiency of insulin due to an excess of adipose tissue. In simple terms there isn’t enough insulin to ‘go around’ all the excess fatty tissue, leading to blood glucose creeping up.
Diagnosis of diabetes
Symptomatic AND one of:
- Fasting glucose > 7.0 mmol/L
- Random glucose > 11.1 mmol/L (or after 75 g OGTT after 2 hrs)
Asymptomatic:
- Above criteria but on two separate occasions
HbA1c:
- > 48 mmol/mol = diagnostic
Diabetes
Why do you get polydipsia and polyuria
Osmotic effect of water being ‘dragged’ out of body due to excess blood glucose being excrete in the urine (glycosuria)
What can cause a misleading HbA1c result?
Increased red cell turnover
DKA
Features
- Abdominal pain
- Polyuria, polydipsia, dehydration
- Kussmaul respiration (deep hyperventilation)
- Acetone-smelling breath (‘pear drops’ smell)
T1DM
Use of HbA1c
- Not as useful in patients with possible/suspected diagnosis of T1DM as it may not accurately reflect a recent rapid rise in serum glucose
T1DM
C-peptide
- Levels are typically LOW in T1DM
Diabetes
Autoantibodies
- Antibodies to glutamic acid decarboxylase (anti-GAD): 80% T1DM
- Islet cell antibodies (ICA, against cytoplasmic proteins in the beta cells): 70-80% T1DM
- Insulin autoantibodies (IAA): 90% of young children with T1DM and 60% of older patients
- Insulinoma-associated-2 autoantibodies (IA-2A)
T1DM
Classic presentations
- Ketosis
- Rapid weight loss
- Age of onset below 50 years
- BMI below 25 kg/m²
- Personal and/or family history of autoimmune disease
How to differentiate T1DM and T2Dm if in doubt?
- Autoantibodies
- C-peptide
T2DM
Use of HbA1c
- > 48 diagnostic of T2DM
- < 48 does not necessarily exclude T2DM
Conditions where HbA1c may not be used for diagnosis
- Haemoglobinopathies
- Haemolytic anaemia
- Untreated iron deficiency anaemia
- Suspected gestational diabetes
- Children
- HIV
- Chronic kidney disease
- People taking meds causing hyperglycaemia (e.g. corticosteroids)