Hyper/Hypothyroid - Clinical Flashcards
What is hypothyroidism?
Underactivity of the thyroid gland (either primary of secondary) which leads to low circulating levels of thyroxine (T4)
What are symptoms of hypothyroidism?
- Tiredness/malaise
- Weight gain
- Poor cold tolerance
- Low mood/poor libido
- Constipation
- Menorrhagia
- Hoarse voice
- Impaired memory/cognition
- Dementia
- Myalgia
- Cramps
- Weakness
What are signs of hypothyroidism?
BRADYCARDIC + neuropathy, myopathy and goitre
- Bradycardia
- Reflexes relax slowly
- Ataxia
- Dry/thin skin/hair
- Yawning/drowsy/coma
- Cold hand +/- cold body
- Ascites +/- non-pititng oedema +/- pericardial/pleural effusion
- Round, puffy face
- Defeated demeanour
- Immobile +/- Ileus
- Congestive cardiac failure
What are primary causes of hypothyroidism?
- Primary atrophic hypothyroidism
- Postpartum thyroiditis
- Hashimoto’s Thyroiditis
- Iodine deficiency
- Post-thyroidectomy
- Drug-induced
- Subacute thyroiditis
What are causes of secondary hypothyroidism?
- Hypopituitarism - very rare
- Cranipharyngioma
- Pituitary tumour
- Isolated TRH deficiency
- Post-pituitary surgery
- Sheehan’s syndrome
What is hashimoto’s thyroiditis?
Form of autoimmune thyroiditis - produces atrophic changes with regeneration, leading to goitre formation. The gland is usually firm and rubbery but may range from soft to hard. Patients may be hypothyroid or euthyroid, though they may go through an initial toxic phase, ‘Hashi-toxicity’.
Who most commonly gets hashimoto’s thyroiditis?
Late middle aged women
What can the thyroid profile of someone with hashimoto’s thyroiditis be?
- Hypo or euthyroid
- Can have “Hashi-toxicity”
What is atrophic hypothyroidism?
Atuoimmune condition associated with antithyroid autoantibodies leading to lymphoid infiltration of the gland and eventual atrophy and fibrosis. The condition is associated with other autoimmune disease such as pernicious anaemia, vitiligo and other endocrine deficiencies. Occasionally intermittent hypothyroidism occurs with subsequent recovery; antibodies which block the TSH receptor may sometimes be involved in the aetiology.
Who is atrophic hypothyroidism more commonly seen in?
Females - 6:1
Do those with atrophic hypothyroidism develop a goitre?
No - leads to atrophy and fibrosis
What age range does Hashimoto’s thyroiditis most commonly occur in?
60-70 yrs
Do those with Hashimoto’s thyroiditis have a goitre?
Yes - lymphocytes are sensitised to the thyroid gland and destroy normal architecture. This destruction in the gland causes a drop in T3 and T4, and a compensatory rise in TSH, which causes goitre development through cellular hyperplasia. Heavy lymphocytic infiltration also adds to the formation of the goitre
What is post-partum thyroiditis?
This is usually a transient phenomenon observed following pregnancy. It may cause hyperthyroidism, hypothyroidism or the two sequentially. It is believed to result from the modifications to the immune system necessary in pregnancy, and histologically is a lymphocytic thyroiditis. The process is normally self-limiting, but when conventional antibodies are found there is a high chance of this proceeding to permanent hypothyroidism.
Why is it important to test TFTs in females experiencing low mood following pregnancy?
They may have post-partum thyroiditis instead of ppost-partum depression
Do those with iodine deficiency have goitre?
Yes - sometimes massive - An iodine level of less than 0.01 mg (10 µg) per day impedes thyroid hormone synthesis. In response to low levels of thyroid hormones, more TSH is produced and secreted via feedback mechanisms, causing cellular hyperplasia
What is subacute thyroiditis?
Temporary hypothyroid phase in someone who was previously hyperthyroid
What investigations would you perform if you suspected hypothyroidism?
- Examination
- Bloods - FBC, U+E’s, TFTs, TPO antibodies, Lipids ALT, CK, Prolactin
Which type of thyroid disease does slow relaxing reflexes occur in?
Hypothyroidism
Why might you do an FBC in someone with suspected hypothyroidism?
Check for anaemia - usually normochromic and normocytic in type but may be macrocytic (sometimes this is due to associated pernicious anaemia) or microcytic (in women, due to menorrhagia)
Why might you look at lipids in someone with suspected hypothyroidism?
May have hypercholesterolaemia
What are the thyroid function tests?
- TSH
- Free T4
- Free T3
Why might you do a prolactin level in someone with suspected hypothyroidism?
They may have hyperprolactinaemia
Why might you look at someones serum creatinine kinase if you suspected hypothyroidism?
Myopathy can cause increased CK levels
What might you find on TFTs in someone with primary hypothyroidism?
- Raised TSH
- Low T3/T4
What might you see on TFTs in someone with secondary hypothyroidism?
- Low TSH
- Low T3/T4
Why is subclinical hypothyroidism?
Low TSH with normal T3/T4 and no clinical symptoms. Risk of progressing to frank hypothyroidism (especially if TPO antibodies present).
How would you manage someone with hypothyroidism?
Levothyroxine - 0-100 mcg/24hrs - Dose depends on the degree of deficiency
If someone was diagnosed hypothyroid and had ischaemic heart disease, what dose of levothyroxine would you start them on?
25 mcg/24hrs
How would you monitor treatment efficacy if treating someone for hypotyroidism with Levothyroxine?
TFTs
how long can it take for full resolution of hypothyroid symptoms?
Up to 6 months
What would an increased TSH and decreased T4 indicate?
Primary Hypothyroidism
What could cause an increased TSH and normal T4?
Treated hypothyroidism or subclinical hypothyroidism
What would cause an increased TSH and T4?
TSH-secreting tumour or thyroid hormone resistance
What would cause increased TSH and T4 and decreased T3?
Slow conversion of T4 -> T3 (deiodonase deficiency)
What would a decreased TSH and increased T4 and T3 indicate?
Primary hyperthyroidism
What would a decreased TSH and T4 indicate?
Secondary hypothyroidism
What is a myxoedema coma?
Severe hypothyroidism leading to decreased mental status, hypothermia, and other symptoms related to slowing of function in multiple organs. It is a medical emergency with a high mortality rate
What are features of a myxoedema coma?
- Hypothermia
- Hyporeflexia
- Hypoglycaemia
- Coma - preceeded by psychosis (myxoedema madness)
- Bradycardia
- Seizures
What might you see on examination of someone suffereing from severe hypothyroidism (myoedema coma)?
- Decreased GCS
- Hypothermia
- Bradycardia
- Hyporeflexia
- Goitre
- Cyanosis
- Hypotension
- Heart failure
What investigations would you do if someone presented with features of a myxoedema coma?
Bloods - FBC, U+E’s Blood cultures, Cortisol, glucose, TFTs, ABG
How would you treat someone suffering from a myxoedema coma?
- O2 - if cyanosed
- Monitor cardiac output - risk of cardiogneic shock
- Correct hypoglycaemia
- IV liothyronine (T3) - slow infusion
- IV Hydrocortisone
- Gradual rewarming
Consider Abx - if infection present
What are the causes of primary hyperthyroidism?
- Graves Disease
- Toxic multinodular goitre
- Acute thyroiditis
- Toxic adenoma
- De Quervan’s thyroiditis
- Post partum thyroiditis