Thyroid Disorders Flashcards by S G

Where is the thyroid gland located?

Anterior neck C5-T1
Below the laryngeal prominence (adams apple)
superior to cricoid cartilage

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Describe the shape of the thyroid gland and blood supply

Butterfly shape 2 lobes- connected in the middle by the isthmus
Superior and inferior thyroid arteries
Superior middle and inferior thyroid veins
Sympathetic innervation

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What is the function of thyroid hormones?

Metabolic regulation..
incr. rate of
lipogenesis and thermogenesis
gluconeogenesis and glycogenolysis
basal metabolic rate
proteinsynthesis
cardiac output
bone resorption

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Which is the more abundant and active form of thyroid hormones?

T4 more abundant
T3 active
T4-> T3 at peripheries

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How do thyroid hormones travel in circulation?

Protein bound as fat soluble
Albumin and thryonine binding globulin

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Thyroid hormones belong to which axis?

Hypothalamic- pituritary - thyroid axis

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What is the difference between hyperthyroidism and thyrotoxicosis?

Hyperthyroidism= overactive thyroid gland
Thyrotoxicosis = excessive thryoid hormone in circulation - may be from incorrect thyroid medication than hyperthyroidism

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What is hyperthyroidism?

Overproduction of thyroid hormone due to thyroid gland over activity

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What is primary hyperthyroidism

Over production of thyroid hormones due to abnormal overactivity of the thyroid gland - thyroid pathology

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What is secondary hyperthyroidism?

Over production of thyroid hormones due to over-stimulation of the thyroid gland from TSH
Pathology of hypothalamus or pituitary

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Describe the epidemiology of hyperthyroidisim?

Women > men
20-40yrs presentation
2.5% women

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What are the general signs and symptoms for hyperthyroidism?

Symptoms…
- Wt loss, anxiety/ irritability, heat intolerance (hot and sweaty)
- hyperphagia, menstrual disturbances, palpitations

Signs
Tachycardia, tremor, thin hair, hair loss, goitre

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What are the general signs and symptoms for hyperthyroidism?

Symptoms…
- Wt loss, anxiety/ irritability, heat intolerance (hot and sweaty)
- hyperphagia, menstrual disturbances, palpitations

Signs
Tachycardia, tremor, thin hair, hair loss, goitre

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What are the Graves specific signs for hyperthyroidism?

Diffuse (smooth) goitre
Grave’s eye disease- exophthalmos- buldging eye due to extraoccular muscle inflam
Pretibital myxoedema- purple/ red symmetrical lesions on anterolater shin

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Describe the pathophysiology for Grave’s disease

Autoimmune condition- IgG serum antibodies
TSH receptor antibodies (TRAb) mimic TSH and bind to TSH receptor on thyroid gland
Increasing thyroid gland stimulation for excess thyroid hormone production
causing smooth goitre, thyroid cell hyperplasia and hyperthryoidism

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Describe the aeitology for hyperthyroidism

Graves disease (2/3rd cases)
Toxic multinodular goitre
Toxic adenoma
Drug induced - amiodarone

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What are the risk factors for hyperthyroidism?

Smoking
Women
HLA - DR3
Amiodarone

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What is the first line drug therapy for hyperthyroidism, action and 2 side effects?

Carbimazole - prevents T4 syntheis
Hypothyroidism and agranulocytosis

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What are the 2 regimes for carbimazole?

Hyperthyriosism
Block and replace- thyroxine and and carbimaole
Titration

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What is the second line drug therapy for hyperthyroidism and its action?

Propylthiourcil, prevents the conversion of t4->t3

What drug can be given to target thesymptoms of hyperthyroidism?

Non-specifc beta blockers eg pronanolol
decr. sympathetic ns activation

Despite drug therapy, what are the other treatments for hyperthyroidism?

Radioiodine (CI pregnancy and breastfeeding)
Thyroidectomy - partial

What is the class of drugs and action for hyperthyroidism

Thionamides - prevent thyroid hormone synthesis

What are the complications of hyperthyroidism?

AF, osteoporosis (thyroid hormones increase bone resorption osteroclast activity incr)

What is thyroid crisis?

Rapid deterioration of thyrotoxicosis so big increase in T4

What are the signs of thyroid crisis?

Hyperpyrexia Tachycardia Delerium, coma and death

What is the treatment of thyroid storm

Large dose of carbimazole propanolol KI (blocks uptake of iodine into thyroid gland)

What are the 3 causes of excess thyroid hormones?

Gland hyperfunction Leakage of preformed hormones Ingested thyroid hromones

What are the investigations and results for hyperthyroidism?

Thyroid function test - Primary = low TSH, high t3/3 - Secondary = high TSH, t3/4 Thyroid antibodies - TRAb = graves specific - TPO = all cases

What is the most common endocrine disorder?

hypothyroidism

What is hypothyroidism?

Deficiency of thyroid hormones due to reduced production from the thyroid gland

What is the difference between primary and secondary (central) hypothyroidism?

Primary is reduced thyroid hormone production due to disorder of the thyroid gland - Raised TSH, low t3/4 Secondary is reduced thyroid hormone production due to disorder or pathology of the pituitary gland or hypothalamus- low TSH, t3/4

Describe the epidemiology of hypothyroidism

More common in womem 2-5% prevelance primary <95% cases

What are the causes of primary hypothyroidism?

- Iodine deficiency - Hashimoto's thyroiditis (common in developed countries) - Drugs- antithyroid, amiodarone, lithium - Thyroidectomy

What are the causes of secondary hypothyroidism?

Hypopituitarism Pit tumour Surgery Drugs eg cocaine

What are the investigations for hypothyroidism?

- TFT: P. High TSH, low T3/4 S. Low TSH, low T3/4 - Thyroid antibodies TPOAb - hashimotos specific - Hyperlipidaemia and hypernatraemia

What is the managment for hypothyroidism?

Levothyroxine (T4) - Life-long - P. titrated for TSH levels to normalise

What are the complications of hypothyroidism?

- coronary heart disease and stroke - dyslipidaemia - p. Incr. risk infertility and miscarriage

What are the signs of hypothyroidism?

Bradycardia Reduced reflexes reaction Ataxia Dry, thin skin and hair Yawning/ coma Cold hand and low temp Ascites Round puffy face Defeated demeanour Immobile and ileus Congestive

What are the symptoms for hypothyroidism?

Wt gain Cold intolerance Fatigue Low mood Hoarse voice Muscle cramps and myalgia Poor memory

What are the risk factors for hypothyroidism?

- Fam/ personal history of autoimmune diseases eg addisons, coeliac, vitiligo, t1dm -thyroidectomy - history iodine def

What are the 5 types of thyroid malignancies?

Papillary Follicular Medullary Lymphoma Anaplastic

What is the clinical presentation of thyroid malignancies?

Dysphagia Hoarse voise Nodules; hard, irregular, incr. size`

What is the treatment for thyrid malignancies?

radioactive iodine surgery thyroxine

What is the differential diagnosis of thyroid malignancy

Goitre

What is Hashimotos thyroiditis?

- Autoimmune condition that can cause hypothyroidism - anti-TPO antibodies and anti-thyroglobulin antibodies cause thyroid inflam. - causes goitre then gland atrophy

How may amiodarone cause hypothyroidism?

It prevents t4 -> t3 in peripheries It has cytotoxic effects on thyroid follicular cells

How may amiodarone cause hyperthyroidism?

High iodine content can cause unregulated thyroid hormone production