Diagnosing Thyroid Dysfunction in Adults in Primary Care Flashcards
When do you test thyroid function
- Patients with signs or symptoms suggestive of thyroid dysfunction
- Patients with a goitre or thyroid nodule.
In what conditions what you recommend offering thyroid function testing to
- Type 1 diabetes or other autoimmune conditions
- atrial fibrillation
- considered for patients with depression or unexplained anxiety
Who is an annual check of thyroid function recommended or
= patients with type 1d diabetes
- down syndrome and turner syndrome
- postpartum thyroiditis women
- neck irradiations
- untreated subclinical hypothyroidism or this ewho have stopped taking their levothyroxine treatments if they have features suggesting underlying thyroid disease
- stopped antithyroid drugs
- patients who have had previous surgery
- patients on long term treatment for hypothyroidism
What patients receive a 6 to 12 monthly check of the thyroid
= patients on lithium therapy
What patients have a 6 monthly check of the thyroid
- patients who have had previous radioiodine treatments
- patients on amiodarone therapy and for the first year following cessation of treatment
What are the signs and symptoms of hypothyroidism
- wekaness
- lethargy
- depression
- weight gain
- cold intolerance
- constipation
- menstrual irregularity
- dry or coarse skin
- hair loss
- myalgia
- eyelid/facial swelling
- deep voice
- bradycardia
- diastolic hypertension
- goitre
What are the symptoms of hyperthyroidism
- irritability and anxiety
- heat intolerance
- excessive sweating
- palpitations
- tremor
- weight loss with increased appetite
- increased bowel frequency
- oligomenorrhoea
- gynaecomastia
- tachycardia
- warm and moist skin
- hair loss
- proximal myopathy
What is a thyroid storm
- signs of decompensated hyperthyroidism
- medical emergency and requires immediate transfer to hospital
what are the signs of a thyroid storm
- high output cardiac failure
- hypertension
- fever
- GI effects including diarrhoea, vomiting, abdominal pain and jaundice
- neurological effects including altered consciousness and rarely seizures
What is toxic mulitnodular goitre
Toxic multinodular goitre arises where there is over-secretion of thyroid hormones from multiple autonomously functioning thyroid nodules, which are almost always benign
What is post viral thyroiditis
De Quervain’s thyroiditis (sometimes called ‘subacute thyroiditis’) causes painful swelling of the thyroid gland
It is believed to be triggered by a viral infection such as mumps or influenza
What is postpartum thyroiditis
- painless condition occurring in the postnatal period
- characterised by a thyrotoxic phase followed by a hypothyroid phase of usually up to several months
Why does the production of thyroid hormones decrease in pregnancy
Pregnancy is a stress test for the thyroid. In normal pregnancy the thyroid gland increases in size by 10%, and the production of thyroid hormones increases by 50%. Placental human chorionic gonadotropin (hCG) has a similar structure to thyroid stimulating hormone (TSH) and cross-reacts with the receptor. This results in reduced plasma TSH levels throughout pregnancy
Whicih pregnant women get thyroid test
- type 1 diabetes - recommended before conception and again at 3 months post party
- previous history of thyroid disease
- current thyroid disease
- family history of thyroid disease
- goitre
- symptoms of hypothyroidism
What are the risk associated with hyperthyrodism in pregnancy
- miscarriage
- gestational hypertension
- prematurity
- low birth weight
- intrauterine growth restrictions
- still birth
- thyroid storm
What are the risks associated with hypothyroidism in pregnancy
- miscarriage
- preterm delivery
- LBW
- gestation hypertension
- impaired fatal neurocognitive development
Name drugs that can affect thyroid function
Amiodarone
Lithium
Describe how amiodarone affects thyroid function
- Induces thyrotoxicosis
Type 1 (20% of cases) is caused by a large iodine load precipitating thyroid autonomy
Type 2 (80% of cases) is a form of destructive thyroiditis and is responsive to steroid treatment.
How does lithium affect thyroid function
Patients taking lithium can experience overt or subclinical hypothyroidism, and a mild self-limiting thyroiditis can occur in a small proportion of patients on initiation of treatment
when do you request TSH alone
- when secondary thyroid dysfunction is not suspected
if TSH is above the reference range…
reference range then measure FT4 in the same sample
If TSH is below the reference range ….
then measure FT4 and FT3 in the same sample
when do you tend to measure TSH and FT4 together
- when there is secondary thyroid dysfunction suspected
Give some common situations when you measure TSH and FT4 together
- diagnosing and monitoring thyroid disorders in pregnancy
- optimising levothyroxine therapy in newly diagnosed patients with hypothyroidism who have persistent symptoms after starting levothyroxine
- monitoring patients with hyperthyroidism in the early months after surgery
Name some rarer situations where you would measure TSH and FT4 together
- diagnosis and monitoring of treatment for central hypothyroidism
- end organ thyroid hormone function resistance
- TSH-secreting pituitary adenomas
why do you not generally recommend routine checks of autoantibodies for thyroid in primary care
- they are neither sensitive or specific for autoimmune thyroid disease
in practise when do you test TOP autoantibodies
- for patients with subclinical hypothyroidism testing TOP autoantibodies is useful in assessing the likelihood of progression to overt hypothyroidism
- if TPO autoantibodies are positive this predicts the likelihood of the patient developing overt hypothyroidism and can guide replacement and further monitoring
what is the difference between total levels of thyroid hormones and free measurements
Totals levels - are total amount of thyroid hormones whereas free are only those that are not bound to proteins
- total hormone levels are affected by alterations in binding proteins that can occur in patients taking oestrogen’s or in pregnancy
what is the difference between overt and subclinical hypothyroidism
Overt primary hypothyroidism
- low FT3
- Low FT4
- Raised TSH
Subclinical hypothyroidism
- normal FT3
- normal FT4
- raised TSH
what is the difference between overt and subclinical hyperthyroidism
Overt primary hyperthyroidism
- raised T3
- raised T4
- low TSH
Subclinical hyperthyroidism
- normal T3
- normal T4
- low TSH
what are the causes of overt primary hypothyroidism
- autoimmune process such as Hashimoto’s disease or atrophic thyroiditis
- radio iodine treatment
- thyroidectomy
What are the causes of subclinical hypothyroidism
- medical interactions
- inadequate replacement after radioactive treatment
- partial thyroidectomy
- iodine deficiency
- thyroid genesis
- ## non thyroidal illness
when should you consider levothyroxine
NICE recommend considering treatment with levothyroxine for patients who have a TSH of 10 mU/litre or higher on two separate occasions three months apart.
- here TSH remains above the reference range but lower than 10 mU/litre, then consider a six month trial of treatment if patients are under 65 and they also have symptoms of hypothyroidism
How often should you monitor patients with subclinical hypothyroidism
Where patients are untreated or have stopped their treatment, then monitor their TSH and FT4 once a year if they have features suggesting underlying thyroid disease, for example previous thyroid surgery or raised thyroid autoantibodie
- reduce monitoring to once very two to three years if they have no underlying thyroid disease
What causes overt primary hyperthyroidism
- Graves
- toxic multinodular goitre
What are the causes of subclinical hyperthyroidism
- graves disease in young patients
- multi nodular goitre and solitary nodules are more common in older patients
When should you refer patients with subclinical hyperthyroidism to the endocrinologist
Patients with confirmed persistent subclinical hyperthyroidism who have two TSH readings lower than 0.1 mU/litre at least three months apart and who also have evidence of thyroid disease (for example, a goitre or positive thyroid antibodies) or symptoms of thyrotoxicosis, require referral to an endocrinologist
What are the long term effects of subclinical hyperthyroidism
- increased risk of AF in people older than 65 with suppressed TSH
- bone mineral density is decreased
what are the long term effects of overt hyperthyroidism
increased bone turnover leading to increased risk of osteoporosis and fracture
How should the level of TSH change during pregnancy from seven to 12 weeks and in the second and third trimester
- 7-12 weeks - Reduce the lower limit of the reference range of TSH by approximately 0.4 mU/L and the upper limit by 0.5 mU/L (corresponding to a TSH reference range of approximately 0.1 mU/L to 4 mU/L)
second and third trimester
- there should be a gradual return of TSH towards the non pregnant normal range
what can be the diagnose with a Low FT and a normal or low TSH (inappropriate)
- Non-thyroidal illness
- Central hypothyroidism (pituitary or hypothalamic disease)
- Assay interference
what can be the diagnosis of a high FT4 with an inappropriately normal or high TSH
- drugs - amiodarone or heparin
- non-compliance with thyroxine replacement
- Thyroid hormone resistance
- TSH secreting pituitary adenoma
- assay interference
what should you not do in central hypothyroidism
it is important not to prescribe levothyroxine while awaiting urgent assessment by an endocrinologist if there is any suspicion of central hypothyroidism. Giving levothyroxine to a patient with hypoadrenalism without first correcting the underlying deficiency of cortisol with glucocorticoid replacement can be life threatening
what is assay interference
This can occur when the presence of heterophilic antibodies in the patient’s blood interfere with the laboratory assay’s ability to detect TSH.
name the symptoms that need an urgent referral (two week rule)
- unexplained hoarseness or voice changes associated with a goitre
- cervical lymphadenopathy associated with a thyroid mass (usually deep cervical or supraclavicular region)
- a rapidly enlarging painless, thyroid mass over a period of weeks
What are symptoms that need a same day referral
stridor associated with a thyroid mass
what is arranged following a referral for cancer
- ultrasound imaging
- fine needle aspiration
How can you treat hypothyroidism in primary care
levothyroxine
what patients with hypothyroidism require referral to an endocrinologists
- central hypothyroidism
- persistant anomalous or discordant thyroid function tests which cannot be explained by an intercurrent illness, medication or assay interference
- any patients with subacute thyroiditis
- patients with pre-exisiting cardiac disease
- patients who you suspect have an uncommon cause of hypothyroidism
- any patient who is pregnant
- patients with postpartum thyroiditis whose thyroid function tests show a hypothyroid pattern
- myxoedema coma
- suggestive symptoms and signs including confusion, hypothermia, hypotension, bradycardia and drowsiness
all patents with ..
hyperthyroidism need referral to an endocrinologists
What should you prescribe for patients with hyperthyroidism who are awaiting a specialist appointment
- prescribe a beta blocker unless contraindicated if they have beat adrenergic symptoms such as tremor or tachycardia, and titrating the dose according to clinical response
