Thyroid disease basics

Question 1

What is meant by thyroid disease?

Answer 1

Thyroid diseases are conditions characterised by a change in thyroid hormone function

Question 2

What are the two categories of thyroid disease?

Answer 2

Primary
Secondary

Question 3

What is meant by primary thyroid disease?

Answer 3

Disease affecting the thyroid gland itself

Question 4

What is meant by secondary thyroid disease?

Answer 4

Disease affecting the hypothalamus or pituitary gland, which causes a resulting change in thyroid function

Question 5

What are some hormones that can be measured in thyroid disease?

Answer 5

Thyroid Stimulating Hormone (TSH)
Free T4
Free T3
Binding proteins

Question 6

Where is TSH released from?

Answer 6

Thyrotroph cells in the anterior pituitary gland

Question 7

What is hypothyroidism?

Answer 7

Insufficient secretion of thyroid hormones from the thyroid gland (Underactive thyroid)

Question 8

What is myxoedema?

Answer 8

Severe hypothyroidism

Question 9

What is pre-tibial myxoedema?

Answer 9

A rare clinical sign of Grave’s disease, an autoimmune thyroid disease which results in hyperthyroidism, causing erythematous plaque formation on the legs

Question 10

What is sub-clinical hypothyroidism?

Answer 10

A condition in which there is high TSH levels, with no clinical symptoms and T3/T4 at normal range

Question 11

What is thyrotoxicosis?

Answer 11

The clincial, physiological and biochemical state arising when tissues are exposed to excess thyroid hormone

Question 12

What is hyperthyroidism?

Answer 12

Refers specifically to conditions in which overactivity of the thyroid gland leads to thyrotoxicosis (Overactive thyroid)

Question 13

What is a goitre?

Answer 13

A goitre is any enlargement of the thyroid gland, caused by impaired synthesis of thyroid hormone

Question 14

What is the most common cause of goitre formation?

Answer 14

This is most commonly due to lack of dietary iodine or lack of bio-availability of iodine

Question 15

How does iodine deficiency lead to goitre formation?

Answer 15

Reduced iodine levels mean there is less iodide present to synthesise T3 and T4

Reduced T3/4 production causes rise in TSH, stimulating gland enlargement, in order to maintain a euthyroid state

Question 16

What are the 2 types of goitre?

Answer 16

• Diffuse (Non-toxic)
• Multi-nodular (Toxic)

Question 17

What are diffuse goitres?

Answer 17

Diffuse goitres are an enlargement of entire thyroid gland, without formation of nodules

Question 18

What are the 2 types of cause of diffuse goitres?

Answer 18

They can be endemic, meaning they occur in >10% of a population, or they can be sporadic

Question 19

What causes endemic diffuse goitre formation?

Answer 19

Endemic diffuse goitres are usually caused by iodine deficiency or goitrogenic substances

Question 20

What are goitrogenic substances?

Answer 20

Goitrogenic substances are those with a very high iodine content such as smoking, disulphides and lithium

Question 21

Where are endemic diffuse goitres most commonly found?

Answer 21

In mountainous regions

Question 22

What are some causes or risk factors of sporadic diffuse goitre formation?

Answer 22

Sporadic diffuse goitres most commonly occur in females and are thought to be associated with puberty

They may also be caused by ingestion of substances limiting T3/4 production or inborn errors of metabolism (Dyshormonogenesis)

Question 23

What is a possible complication of dyshormonogenesis in children?

Answer 23

Cretinism

Question 24

How do diffuse goitres usually present?

Answer 24

Diffuse goitres usually don’t cause changes in thyroid hormone levels, but instead present with mass effects

Question 25

What is the main cause of multi-nodular goitre formation?

Answer 25

Multi-nodular goitres usually evolve from longstanding, simple goitres via recurrent hyperplasia and involution

Question 26

Describe the pathology of multi-nodular goitre formation

Answer 26

Mutations of TSH signalling pathways in the thyroid lead to variation of response of follicular cells to external stimuli, as well as formation of fibrous bands, causing nodule formation

Question 27

What are some possible complications of multi-nodular goitre?

Answer 27

This can lead to follicular rupture, haemorrhage, scarring and calcification, as well as mass effects
They may also develop into an autonomous nodule, leading to hyperthyroidism

Question 28

What are some examples of mass effects caused by goitre formation?

Answer 28

• Cosmetic changes
• Airway obstruction
• Vessel compression

Question 29

How can thyroid disease affect conception?

Answer 29

Hypothyroidism and hyperthyroidism causes anovulatory cycles which can reduce fertility

Anovulatory cycles are menstrual cycles in which there is no luteal phase or ovulation

Question 30

Why does pregnancy increase demand on the thyroid?

Answer 30

Maternal thyroxine is important for neonatal development, especially of the CNS

This means that during pregnancy, there is an increased demand on the thyroid during pregnancy