Thyroid

Question 1

What hormones can be measured to screen for thyroid disease?

Answer 1

TSH

T3 and 4

Question 2

What hormone levels would you expect to find in hyperthyroidism?
What is the exception?

Answer 2

Low TSH
High T3&4
A pituitary adenoma secretes TSH, in which case TSH is high.

Question 3

What hormone levels would you expect to find in hypothyroidism?
What is the exception?

Answer 3

High TSH
Low T3&4
Secondary hypothyroidism is the exception e.g. a pituitary or hypothalamic cause of the hypothyroid, in which case TSH would be low.

Question 4

What does thyrotoxicosis mean?

Answer 4

An abnormal and excessive quantity of thyroid hormone in the body.

Question 5

Where is the pathology in primary hyperthyroidism?

Answer 5

Thyroid itself is behaving abnormally and producing excessive thyroid hormone.

Question 6

Where is the pathology in secondary hyperthyroidism?

Answer 6

The hypothalamus or pituitary.

The thyroid is producing excessive thyroid hormone as a result of overstimulation by thyroid stimulating hormone.

Question 7

Describe Grave’s disease

Answer 7

Autoimmune condition where TSH receptor antibodies cause a primary hyperthyroidism.

Question 8

Describe toxic multinodular goitre (Plummer’s disease)

Answer 8

A condition where nodules develop on the thyroid gland that act independently of the normal feedback system and continuously produce excessive thyroid hormone. Primary hyperthyroidism .

Question 9

What are the causes of hyperthyroidism?

Answer 9

Grave’s disease
Toxic multinodular goitre
Solitary toxic thyroid nodule
Thyroiditis (e.g. De Quervain’s, Hashimoto’s, postpartum and drug-induced thyroiditis)

Question 10

What are the signs of hyperthyroidism specific to Grave’s?

Briefly describe the common pathophysiology

Answer 10

Reactions to the TSH receptor antibodies:
>Bilateral exophthalmos.
-inflammation, swelling and hypertrophy of the tissue behind the eyeball that forces the eyeball forward.
>Pretibial myxoedema.
-a dermatological condition where there are deposits of mucin under the skin on the anterior aspect of the leg (the pre-tibial area). This gives a discoloured, waxy, oedematous appearance to the skin over this area.
>Diffuse goitre, without nodules
>Graves’ eye disease.

Question 11

What are the features of hyperthyroidism?

Answer 11

Anxiety and irritability
Sweating and heat intolerance
Tachycardia
Weight loss
Fatigue
Frequent loose stools
Sexual dysfunction

Question 12

What are the signs of hyperthyroidism specific to toxic multinodular goitre?

Answer 12

Goitre with firm nodules.

Most patients are aged over 50.

Question 13

Briefly describe De Quervain’s Thyroiditis

Answer 13

the presentation of a viral infection with fever, neck pain and tenderness, dysphagia and features of hyperthyroidism.
There is a hyperthyroid phase followed by a hypothyroid phase as the TSH level falls due to negative feedback.

Question 14

Briefly describe how to manage De Quervain’s Thyroiditis

Answer 14

It is a self-limiting condition.
Supportive treatment:
NSAIDs for pain and inflammation.
Beta-blockers for symptomatic relief of hyperthyroidism.

Question 15

Briefly describe the meaning of a thyroid storm

Answer 15

“thyrotoxic crisis”. It is a more severe presentation of hyperthyroidism with pyrexia, tachycardia and delirium.

Question 16

What is the first line treatment of hyperthyroidism?

Answer 16

Carbimazole is the first line anti-thyroid drug.

Question 17

What is the second line pharmacological treatment of hyperthyroidism?

Answer 17

Propylthiouracil is the second line anti-thyroid drug. It is used in a similar way to carbimazole.
There is a small risk of severe hepatic reactions, including death, which is why carbimazole is preferred.

Question 18

What pharmacological options are there for symptom control of hyperthyroidism?

Answer 18

Beta blockers are used to block the adrenalin related symptoms of hyperthyroidism.
Propranolol is a good choice because it non-selectively blocks adrenergic activity as opposed to more “selective” beta blockers the work only on the heart.

Question 19

What are the non-pharmacological treatment options of hyperthyroidism?

Answer 19

Treatment with radioactive iodine involves drinking a single dose of radioactive iodine. This is taken up by the thyroid gland and the emitted radiation destroys a proportion of the thyroid cells. Patients can be left hypothyroid afterwards and require levothyroxine replacement.
A definitive option is to surgically remove the whole thyroid or toxic nodules. Patients can be left hypothyroid afterwards and require levothyroxine replacement.

Question 20

What are the causes of primary hypothyroidism?

Answer 20

Hashimoto’s Thyroiditis
Iodine Deficiency
Secondary to Treatment of Hyperthyroidism
Medications- Lithium inhibits the production of thyroid hormones in the thyroid gland and can cause a goitre and hypothyroidism.
- Amiodarone interferes with thyroid hormone production and metabolism, usually causing hypothyroidism but it can also cause thyrotoxicosis.

Question 21

What are the causes of Secondary Hypothyroidism?

Answer 21

Hypopituitarism:
Tumours
Infection
Vascular (e.g. Sheehan Syndrome)
Radiation

Question 22

Describe the presentation of hypothyroidism

Answer 22

Weight gain
Fatigue
Dry skin
Coarse hair and hair loss
Fluid retention (oedema, pleural effusions, ascites)
Heavy or irregular periods
Constipation

Question 23

Describe the cause of Hashimoto’s thyroiditis

Answer 23

Autoimmune inflammation of the thyroid gland.

It is associated with antithyroid peroxidase (anti-TPO) antibodies and antithyroglobulin antibodies.

Question 24

Describe the management of hypothyroidism

Answer 24

Oral levothyroxine: synthetic T4. This metabolizes to T3 in the body.
The dose is titrated until TSH levels are normal.
(If the TSH level is high, the dose is too low and needs to be increased.)

Question 25

Describe the relevant thyroid antibodies

Answer 25

Anti-TPO antibodies are antibodies against the thyroid gland itself.
>Usually present in Grave’s Disease and Hashimoto’s Thyroiditis
Antithyroglobulin Antibodies are antibodies against thyroglobulin, a protein produced and extensively present in the thyroid gland.
>Can be present in normal individuals. Usually present in Grave’s Disease, Hashimoto’s Thyroiditis and thyroid cancer.
TSH Receptor Antibodies are autoantibodies that mimic TSH.
>The cause of Grave’s Disease and so will be present in this condition.

Question 26

What investigations of the thyroid gland can be done?

Briefly describe the imaging available.

Answer 26

TSH, T3, T4.
Antibodies.
Thyroid ultrasound (for thyroid nodules and distinguishing between cystic and solid nodules).
Radioisotope scans (used to investigate hyperthyroidism and thyroid cancers)
Gamma rays show radioactive iodine taken up by the thyroid.
-Diffuse high uptake is found in Grave’s -Disease
Focal high uptake is found in toxic multinodular goitre and adenomas
-“Cold” areas (i.e. abnormally low uptake) can indicate thyroid cancer