Thyroid disease Flashcards by Beth Mickel

what is primary thyroid disease

disease affecting the thyroid gland itself

can occur with or with our goitre

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what is secondary thyroid disease

thyroid gland is fine

something else isn’t working eg. hypothalamus or pituitary gland disease

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what is TSH

a hormone secreted by the pituitary gland to stimulate thyroid hormone secretion in the thyroid

(Also called thyrotrophin)

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What percent of thyroid hormone is T4

80%

T4 is not active and gets changed to T3 in the cells

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What percent of thyroid hormone is T3

20%

4x more potent

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what transporter hormones do T3 and T4 bind to

Thyroxine binding globulin
thyroxine binding pre-albumin
albumin

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where is most of the T4 converted to T3

The liver

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what happens to free T3 and T4 and thyroid stimulating hormone in primary hypothyroidism

Low T3 and T4

High TSH to try and increase the thyroid hormone levels

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what happens to free T3 and T4 and TSH in primary hyperthyroidism

Free T3/4 is high

TSH drops to try and stop the thyroid gland producing too much thyroxine

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what happens to T3/4 and TSH in secondary hypothyroidism

reduces TSH production (due to something in the pituitary or hypothalamus not working)

subsequently also had low T3/T4

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what happens to T3/4 and TSH in secondary hyperthyroidism

vvv rare - due to a problem in pituitary gland where TSH is secreted too much and doesn’t respond to negative feedback (could be from a rare tumour)

TSH is high so free T4/T3 is high

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what does hypothyroidism describe

any disorder resulting in insufficient secretion of thyroid hormones

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what does myxoedema describe

severe hypothyroidism and is a medical emergency (severe under active)

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what does pretibial myxoedema describe

Rare clinical sign of grave’s disease which results from hyperthyroidism

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what populations have higher incidence of hypothyroidism

white populations
women
older

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what causes goitrous primary hypothyroidism

chronic thyroiditis (Hashimoto's thyroiditis) 
iodine deficiency 
Drug induces 
maternally transmitted (mum on anti-thyroid drugs when pregnant) 
Hereditary biosynthetic defects

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what causes non-goitrous primary hypothyroidism

atrophic thyroiditis
positive-ablative therapy (radio iodine, surgery)
post-radiotherapy
congenital defect

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what causes SECONDARY hypothyroidism

disease of the pituitary and hypothalamus 
glands 
-infiltrative 
-infectious 
-malignant 
-traumatic
-congenital 
-cranial radiotherapy 
-drug-induced

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what is autoimmune hypothyridism

autoimmune conditions which attack the hypothalamus and pituitary

most common cause in western world

often family history

antibodies against thyroid peroxidase (TPO)

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what are the 3 stages in the progression of hypothyroidism

euthyroid

mild thyroid failure

overt hypothyroidism

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what are some clinical features of hypothyroidism

hair and skin

coarse, sparse hair
dull expressionless face
periorbital puffiness
pale cool skin that feels doughy to touch
vitiligo may be present
hypercarotenaemia

cold intolerance

pitting oedema

reduced heart rate
cardiac dilation
pericardial effusion
worsening of heart failure

hyperlipidaemia

decreased appetite
weight gain

constipation

deep house voice
macroglossia
obstructive sleep apnoea

decreases intellectual and motor activities 
muscle stiffness, cramps 
peripheral neuropathy 
prolongation of tendon jerks 
carpal tunnel

heavier periods

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What are the lab investigations seen in hypothyroidism

Increased TSH
Decreased free T4/3

increases macrocytosis
increases creatine kinase
increases LDL-cholesterol
hypoantaemia (decreases renal water loss)
hyperprolactinaemia (increased TRH increases PRL)

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what are they thyroid autoantibodies

anti-TPO antibody (autoimmune hypothyroidism)
anti-thyroglobulin antibody
TSH receptor antibody (graves)

how is hypothyroidism managed

normal metabolic rate should be restored gradually - may lead to cardiac arrhythmia

younger patients - start levothyroxine at 50-100micrograms daily

start elderly patients on levothyroxine 25-50 micrograms daily adjusted evert 4 weeks according to response

check TSH 2 months after any dose change

once stabilised check TSH every 12-18 months

what is levothyroxine

How do you treat secondary hypothyroidism

TSH unreliable | titrate does of levothyroxine to the free t4 level

when is levothyroxine taken

preferably before breakfast

what happens to dose requirements in pregnancy

25-50% increase in dose of levothyroxine

what is myxoedema coma

typically affects older women with a long standing unrecognised/untreated hypothyroidism morality up to 60% bradycardia, type 2 respect failure and co-existing adrenal failure

how to treat myoxeoedema coma

``` intensive care passively rewarm cardiac monitoring for arrythmia close monitoring of urine output broad spec antibiotics causes thyroxine ```

what is thyrotoxicosis

state arriving when tissues are exposed to too much thyroid hormone

what is hyperthyroidism

specifically conditions in which overactivity of the thyroid gland leads to thyrotoxicosis

symptoms and signs of thyrotoxicosis

Cardiac palpitation, atrial fibrillation cardiac failure (v rare) Sympathetic tremor, sweating CNS anxiety, nervousness, irritability, sleep disturbance GI frequent, loose bowel movement vision lid retraction double vision proptosis (graves) hair and skin brittle, thin hair rapid fingernail growth reproductive menstrual cycle changes (lighter, less frequent) muscles weakness especially in thighs and upper arms Metabolism weight loss and increases appetite Thermogenesis intolerance to heat

what are come hyperthyroid causes of thyrotoxicosis

hyperthyroidism excessive thyroid stimulation - Graves - hashitoxicosis - thyrotropinoma - thyroid cancer - choriocarcinoma thyroid nodules with autonomous function - toxic solitary nodule - toxic multi nodular goitre

What are some causes of thyrotoxicosis which aren't associated with hyperthyroidism

Thyroid inflammation - subacute thyroiditis - post-partum thyroiditis - drug induced exogenous thyroid hormones - over treatment with levothyroxine - thyrotoxicosis facitia ectopic thyroid tissue - metastatic carcinoma - stuma ovarii

Who gets graves disease

younger 20-50 years more common in females smoking is important -harder to treat, increases risk of eye disease combination of genetic susceptibility and environmental factors

investigations in Graves disease

``` Decreases TSH (often 0) high free T3/4 ``` increased alkaline phos and hypercalcaemia decreased white cell count TSH receptor antibody (TRAb) -no need to image thyroid gland if this is found - can confidently make diagnosis

What is pretibial myxoedema

bumpy red rash on lower limbs only seen in graves disease v rare

what is thyroid acropachy

severe nail clubbing seen in graves | v v rare

what is a thyroid bruit

sign of graves disease (only) associated with large goitres reflective of a hyper vascular thyroid escalate over the thyroid

What is Grave's eye disease

``` occurs in 20% of graves patients TRAb driven pathophysiology can be unilateral most is mild and treated with eye drops more severe can require use of steroids, radiotherapy or surgery ```

What is nodular thyroid disease and who gets it

seen in older patients insidious onset thyroid feels nodular asymmetrical goitre

what tests do you do for nodular thyroid disease

``` increased Free T4/3 decreased TSH antibody NEGATIVE (TRAb) Scintigraphy (thyroid uptake scan)- high uptake thyroid ultrasound ```

what is thyroid storm/crisis

severe clinical presentation of an overactive thyroid/thyrotoxicosis occurs in people with underlying graves disease who are exposed to a 'second hit' eg. infection, surgery

Treatment for hyperthyroidism

anti-thyroid drugs (ATDS)

first line drug for hyperthyroidism

Carbimaxole once daily lower rate of side effects compared to PTU risk of aplasia cutis in early pregnancy

What is the 1st line drug for hyperthroidism in the first trimester of pregnant

Propylthiouracil (PTU) twice daily 10x less potent

side effects of antithyroid drugs

generally well tolerated 1-5% will develop allergic type reactions - rash, urticaria, arthralgia cholestatic jaundice, increased liver enzymes, hepatic failure Agranulocytosis (rare, happens in first 6 weeks)

what drug can you give to help the symptoms of hyperthyroidism

b-blockers propranolol is the drug of choice use in caution with those in asthma - CCB can be used instead

what is radio iodine treatment

1st choice treatment for relapsed graves disease and nodular thyroid disease safe, no increased risk of thyroid cancer

when is thyroidectomy done

when radio iodine is contraindicated

what effect does amiodarone have on the thyroid

can cause hypo or hyper thyroids

what is subclinical hypothyroidism

increased TSH but with normal free T3/4

what is subclinical hyperthyroidism

Decreased TSH | normal free T3/4

what is such euthyroid syndrome

encountered in the unwell, hospitalised patients | impact of intercurrent illness on the hypothalamus??