Hypothyroidism

Question 1

Difference between primary and secondary hypothyroidism

Answer 1

Primary - hypothyroidism arising due to pathology of the thyroid itself or attack of the thyroid

Secondary - hypothyroidism arising due to pathology of an upstream process

Question 2

Example of a process leading to secondary hypothyroidism

Answer 2

Hypopituitarism with isolated TSH deficiency - leads to low TSH levels and low T3/4 levels

Question 3

What is the leading cause of hypothyroidism?

Answer 3

Autoimmunity

Question 4

Give the three primary types of autoimmunity-mediated hypothyroidism

Answer 4

Atrophic
Hashimoto’s
Postpartum

Question 5

Discrimination between Hashimoto’s thyroiditis and atrophic hyperthyroidism.

Answer 5

Presence of goitre in Hashimoto’s vs no goitre in atrophic hypothyroidism

Question 6

Which white blood cell is predominantly featured in autoimmunity-mediated thyroiditis?

Answer 6

Lymphocytes

Question 7

Which white blood cell is predominantly featured in autoimmunity-mediated thyroiditis?

Answer 7

Lymphocytes

Question 8

Which auto-antibody is often detected in individuals with autoimmune thyroiditis?

Answer 8

anti(TPO)

Question 9

What can postpartum thyroiditis be mistaken for, and what tests can be used to delineate between the two?

Answer 9

Misdiagnosed as postnatal depression;

Thyroid function tests used to differentiate

Question 10

Congenital causes of hypothyroidism.

Answer 10

Agenesis

Ectopic thyroid remnants

Dyshormogenesis

Question 11

Defects of hormone synthesis causing hypothyroidism.

Answer 11

Iodine deficiency

Dyshormogenesis

Anti-thyroid drugs

Other drugs (e.g. lithium, amiodarone, interferon)

Question 12

Post-surgical mechanisms of hypothyroidism

Answer 12

Radioactive iodine therapy

External neck irradiation

Tumour infiltration

Question 13

Signs and symptoms of hypothyroidism

Answer 13

General tiredness/malaise

Weight gain

Goitre (with Hashimoto’s)

Depression

Psychosis

Dry hair/skin

Mental slowness

Ataxia

Bradycardia

Oedema

Deep voice

Constipation

Anorexia

Question 14

Investigation of choice for hypothyroidism

Answer 14

Serum TSH

High TSH confirms primary hypothyroidism

Low free T4 level confirms the hypothyroid state (and is essential to exclude TSH deficiency)

Question 15

Other investigations for hypothyroidism

Answer 15

Anaemia: normochromic and normocytic in type, but may be macrocytic (pernicious anaemia) or microcytic (menorrhagia or coeliac disease)

Increased serum aspartate transferase levels from muscle and/or liver

Increased serum creatinine kinase levels with associated myopathy

Hypercholesterolaemia and hypertriglyceridemia

Hyponatraemia due to increase in ADH and impaired water clearance

Question 16

Management of hypothyroidism

Answer 16

Replacement therapy with levothyroxine for life

Starting dose dep. on patient history (100 mg for fit and young, 50 mg for small, old, or frail). Lower still for people with ischaemic heart disease

People with ischaemic heart disease will require serial ECGs and intervention if required

T4 and TSH levels monitored regularly (annual function test once stabilised)