Hyperthyroidism

Question 1

Level of the thyroid?

Answer 1

Anterior neck

Between C5 and T1

Question 2

How many lobes? What connects them?

Answer 2

Two

Isthmus

Question 3

Anatomical location of the thyroid
Behind…?
Wrapping around…?
Inferior to…?

Answer 3

Behind the sternohyoid and sternothyroid muscles
Wrapping around the cricoid cartilage and superior tracheal rings
Inferior to the thyroid cartilage of the larynx

Question 4

Blood supply to the thyroid

Answer 4

Superior thyroid artery (branch of external carotid artery)

Inferior thyroid artery (branch of thyrocervical trunk)

Question 5

Venous drainage to the thyroid

Answer 5

Superior, middle and inferior thyroid veins

- drains into internal jugular veins and brachiocephalic veins

Question 6

When operating on the thyroid, care must be taken to not damage which nerve?

Answer 6

Recurrent laryngeal nerves

Question 7

Define goitre

Answer 7

Swelling of the neck due to enlargement of thyroid gland

Question 8

Causes of diffuse goitre (5)

Answer 8

Physiological (pregnancy/puberty)
Graves’ disease
Hashimoto’s thyroiditis
Subacute (de Quervain’s) thyroiditis
Iodine deficiency

Question 9

Causes of nodular goitre (3)

Answer 9

Toxic multinodular goitre
Adenoma
Carcinoma

Question 10

Most common cause of thyrotoxicosis

Answer 10

Graves’

Question 11

Graves’ typical presentation

Answer 11

Women aged 30-50, signs of thyrotoxicosis, exopthalmos, ophthalmoplegia, pretibial myxoedema, thyroid acropachy

Question 12

Pathology of Graves

Answer 12

Circulating IgG auto-antibodies binding to and activating G-protein-coupled thyrotropin receptors, which causes smooth thyroid enlargement and increased hormone production.

Question 13

What are the blood results for Graves?

Answer 13

TSH receptor stimulating antibodies
Anti-thyroid peroxidase antibodies
Low TSH
High T4

Question 14

Features of a thyroid storm

Answer 14

tachycardia, fever, atrial fibrillation, heart failure, fever, diarrhoea, vomiting, dehydration, jaundice, agitation, delirium, and coma

Question 15

Define hyperthyroidism

Answer 15

Excess of circulating thyroid hormones (thyrotoxicosis) is produced by an overactive thyroid gland

Question 16

How are thyroid hormone levels normally controlled?

Answer 16

Negative feedback on the hypothalamus and pituitary gland

Hypothalamus secretes thyrotropin-releasing hormone (TRH) which stimulates the anterior pituitary to secrete thyroid-stimulating hormone (TSH). This then acts on the thyroid to increase production of thyroxine and triiodothyronine.

Question 17

Overt vs subclinical hyperthyroidism

Answer 17

Overt = TSH is suppressed and free thyroxine or free triiodothyronine concentrations are above the normal reference range

Subclinical = TSH supressed but normal FT4 and FT3

Question 18

Causes of hyperthyroidism

Answer 18

Graves
Toxic multinodular goitre
Adenoma
Drugs - iodine, lithium, interferon alpha, thyroxine, corticosteroids
High levels of HCG - e.g. multiple pregnancy, women with hyperemesis, tumour
Pituitary adenoma
Thyroid hormone resistance syndrome
Subacute (de Quervain's) thyroiditis
Acute thyroiditis
Post-partum thyroiditis

Question 19

Symptoms of hyperthyroidism (general)

Answer 19

Hyperactivity, emotional lability, insomnia, irritability, anxiety, palpitations.
Exercise intolerance, fatigue, muscle weakness.
Heat intolerance, increased sweating.
Increased appetite with weight loss (or occasionally weight gain), diarrhoea.
Infertility, oligomenorrhoea, amenorrhoea.
Polyuria, thirst, generalized itch.
Reduced libido, gynaecomastia in men.
Deterioration in blood glucose control and hyperglycaemia in people with diabetes mellitus.

Question 20

Signs and symptoms of de Quervain’s

Answer 20

Rapid-onset malaise, fever, and thyroid pain which may extend to the jaw, ears, or throat
Tender, enlarged, firm, irregular thyroid (usually diffuse)

Question 21

Signs and symptoms of toxic multinodular goitre

Answer 21

Breathlessness, dysphagia, neck pressure

Non-tender thyroid nodules

Question 22

Signs of hyperthyroidism

Answer 22

Agitation, fine tremor, warm moist skin, palmar erythema.
Sinus tachycardia, atrial fibrillation, heart failure, dependent oedema.
Eye signs (lid lag or retraction).
Goitre or nodule(s)
Bruit
Onycholysis and thyroid acropachy
Pruritus, urticaria, vitiligo, diffuse alopecia, thyroid dermopathy, pretibial myxoedema
Muscle wasting, proximal myopathy, hyper-reflexia.
Splenomegaly, lymphadenopathy.
Gynaecomastia in men.

Question 23

Investigations for hyperthyroidism

Answer 23

TFTs - TSH, FT4, FT3

ESR and CRP if suspect subacute thyroiditis

Question 24

How to manage overt hyperthyroidism in primary care

Answer 24

Admit as a medical emergency a person with symptoms of thyroid storm.

Refer using a suspected cancer pathway (for an appointment within 2 weeks) if a person has a thyroid nodule or goitre and malignancy is suspected.

Refer all other people with overt hyperthyroidism to an endocrinologist for further investigations and management.

Consider prescribing a beta-blocker while waiting and titrating the dose depending on clinical response), to provide relief of adrenergic symptoms (for example tremor or tachycardia).

Question 25

Radionuclide thyroid uptake scan in Graves'

Answer 25

Diffuse pattern of uptake in Graves' disease

Question 26

Radionuclide thyroid uptake scan in toxic nodular goitre

Answer 26

One or more 'hot' nodules, patchy uptake

Question 27

Radionuclide thyroid uptake scan in de Quervain's thyroiditis

Answer 27

Reduced or absent uptake of radioisotope into the thyroid

Question 28

Specialist drug treatments for hyperthyroidism

Answer 28

Carbimazole and propylthiouracil - Used short term before surgery, or medium-term to induce remission in Graves' (4-8 weeks), or long-term if other options contraindicated. When euthyroid, can use titration-block regime (thionamide used and dose adjusted every 4-6 weeks) or block and replace regime (a thionamide is used to block the synthesis of thyroid hormone and levothyroxine is added when the FT4 is in range).

Question 29

How does radioiodine treatment work?

Answer 29

Induces damage of DNA leading to death of thyroid cells

Question 30

Surgical treatment for hyperthyroidism

Answer 30

Total or near-total thyroidectomy

Question 31

Thyroidectomy post-op complications

Answer 31

Hypothyroidism, hypocalcaemia due to hypoparathyroidism (often transient), and vocal cord paresis due to damage to the recurrent laryngeal nerve.

Question 32

When to treat subclinical hyperthyroidism?

Answer 32

If TSH level persistently equal to or less than 0.1 mU/L, if they are aged 65 years or older, are postmenopausal, are at risk of osteoporosis, have cardiac risk factors, or have possible symptoms of hyperthyroidism.

Question 33

Complications of hyperthyroidism

Answer 33

``` Graves' orbitopathy Thyroid storm Atrial fibrillation Heart failure Reduced bone mineral density Increased mortality rate Anxiety and depression Thyrotoxic periodic paralysis Increased risk of complications in pregnancy ```

Question 34

De Quervain's pathology/stages

Answer 34

Thought to occur after a viral infection Phases: 1. Hyperthyroidism, painful goitre, raised ESR (lasts 3-6 weeks) 2. Euthyroid (1-3 weeks) 3. Hypothyroidism (weeks-months) 4. Thyroid structure and function goes back to normal

Question 35

Management of De Quervain's

Answer 35

Usually self-limiting - refer to specialists

Question 36

Toxic multinodular goitre pathology

Answer 36

Autonomously functioning thyroid nodules that secrete excess thyroid hormones

Question 37

Causes of thyroid enlargement in euthyroid patient

Answer 37

Solitary thyroid nodule – cyst, adenoma, discrete nodule in MNG or malignant Sarcoid TB

Question 38

How does carbimazole work?

Answer 38

Used to decrease thyroid hormone synthesis, by acting as a preferred substrate for iodination by thyroid peroxidase (key enzyme in thyroid hormone synthesis)

Question 39

Important adverse effect of carbimazole

Answer 39

Agranulocytosis