Preparation for Glucose Tolerance Test
- overnight fast of 8-14 hours
- 3 days of unrestricted diet + exercise
- evening meal as normal
What happens during the glucose tolerance test?
- fasting blood in the morning
- Drink 75 g of anhydrous glucose in 250-300ml water over 5 mins
- blood sample 2 hours later
- no smoking during the test
Diagnosis of diabetes using GTT
- random venous plasma glucose = 11.1 mmol/l
- fasting venous plasma glucose = 7.0 mmol/l
- 2 hr post = 11.1 mmol/l
What is HbA1c?
- percentage of glycosylated haemoglobin
- estimate for 90 days
Diagnostic value of Diabetes using HbA1c
- Pre-diabetes
- > 42 - 47 mmol/mol
- fasting plasma glucose 6 - 7 mmol
- Diabetes
- > 48 mmol/mol
- fasting plasma glucose > 7 mmol
T2DM diagnosis using HbA1c
- HbA1c > 48 mmol + symptomatic
2. HbA1c > 48 mmol + asympotamtic –> repeat within 2 weeks —> HbA1c > 48 mmol
When can you not use HbA1c to diagnose diabetes?
- Under 18yrs
- Possible Type 1
- Where glucose may rise rapidly e.g.: steroids, antipsychotics.
- Reduced red cell survival e.g. haemolytic anaemia
- Gestational Diabetes
- Pancreatic damage/surgery
- Anaemia/Haemoglobinopathy
Define hypoglycaemia?
- Development of neurogenic or neuroglycopenic symptoms
- Low blood glucose (<4 mmol/L if on insulin or secretagogue)
- Response to carbohydrate load
What are neurogenic symptoms?
Trembling Palpitations Sweating Anxiety Hunger Nausea
What are neuroglycopenic symptoms?
Difficulty Concentrating Confusion Weakness Drowsiness Vision Changes Difficulty Speaking Dizziness
Define severe hypogylcaemia
- Requires the assistance of another person
- Unconsciousness may occur
- Plasma glucose is typically <2.8 mmol/L
Clinical indications for TFTs (hyper)
- Rapid-onset malaise, fever, and thyroid pain (may suggest subacute thyroiditis).
- Compression symptoms of breathlessness, hoarse voice, dysphagia, neck pressure (may be caused by a toxic multinodular goitre).
- Agitation, emotional lability, insomnia, irritability, anxiety, palpitations.
- Exercise intolerance, fatigue, muscle weakness.
- Heat intolerance, increased sweating.
Increased appetite with unintentional weight loss, diarrhoea. - Subfertility, oligomenorrhoea, amenorrhoea.
- Polyuria, thirst, generalized itch.
- Reduced libido, gynaecomastia in men.
- Deterioration in blood glucose control and hyperglycaemia in people with diabetes mellitus
Interpret TFTs
Primary hypothyroidism:
- Low T3/T4
- High TSH
Primary hyperthyroidism:
- High T3/T4
- Low TSH
Secondary hypothyroidism:
- Low T3/T4
- Low/Normal TSH
Secondary hyperthyroidism:
- High T3/T4
- High TSH
Subclinical thyroid
Hypo:
Normal T3/T4
High TSH
Hyper:
Normal T3/T4
Low TSH
1st line for thyroid nodules
USS
- follow-up dependent on US appearances
USS classification of thyroid nodules
U1 = normal U2 = benign U3 = indeterminate U4 = Suspicious U5 = malignanct
Which thyroid nodule require fine-needle biospy (FNAB)?
- U3-U5 = USS guided FNAB
- FNA of abnormal lymph nodes
- Incidental nodules on CT
- PET-CT positive nodules
THY classification: cytology + action
Thy 1:
Cyt = Non-diagnostic US
Action = +/- repeat FNA
Thy 2:
Cyt = Non-neoplastic
Action = Correlate with clinical and US
findings
Thy 3a: Cyt = Neoplasm possible (atypical features) Action = Further US +/- FNA MDT discussion if Thy3a on repeat sample
Thy 3f
Cyt = Follicular neoplasm Action = Diagnostic hemi-thyroidectomy
Thy 4:
Cyt = Suspicious of malignancy
Action = Diagnostic hemi-thyroidectomy
Thy 5:
Cyt = Diagnostic of malignancy
Action = Therapy appropriate to tumour
type: usually surgery
When is synacthen test requested?
Suspecting addison’s disease:
Crisis:
1. hypotension, hypovolaemic shock, delirium, reduced consciousness, acute abdominal pain, vomiting, headache, low-grade fever, and muscle weakness.
- Hypoglycaemia can also occur (in particular in children).
Persistent, non-specific clinical features:
1. Fatigue
- Hyperpigmentation
- GI: weight loss, loss of appetite and premature satiety, nausea and vomiting, abdominal pain, and/or cravings for salt.
- MSK: muscle weakness (difficulty getting up from sitting or carrying weights), muscle cramps (due to electrolyte derangement), and joint pain.
- CVS: postural dizziness due to hypotension (blood pressure decrease of 20 mmHg between sitting and standing measurements).
- Other: headache, low-grade fever, increased thirst or urination, loss of axillary or pubic hair in women, and anxiety or depression.
How is synacthen test carried out?
- Get baseline level
- Inject 250mg of Tetracosactrin(IV or IM)
- Measure plasma cortisol level in 60 minutes
- Excluded if basal or test level is > 525 nmol/L
Plasma cortisol levels between 8am-9am
- Level <83 nmol/Llikely
- Level >525 nmol/L rules OUT
When should you suspect adrenal crisis?
Unexplained hyponatremia and hyperkalemia in the setting of hypotension unresponsive to catecholamine and fluid administration
What is the diagnostic test for acromegaly?
first line: Serum IGF-1 levels
Oral Glucose tolerance to confirm diagnosis
pituitary MRI may show pituitary tumour
Clinical features of hyperprolactinemia
- Infertility
- Changes in menstruation.
- Galactorrhoea.
- Women who are not pregnant or nursing may begin producing breast milk.
- Loss of libido
- Gynaecomastia
- impotence
- Headaches or eye problems caused by the enlarged pituitary pressing against nearby eye nerves.
Diagnostic test for prolactinoma
MRI
