3. Thyroid Dysfunction Flashcards Preview

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Flashcards in 3. Thyroid Dysfunction Deck (26):

What attaches the thyroid gland to the trachea and larynx?

The pretracheal fascia . Thus the thyroid moves upwards on swallowing an important diagnostic feature for lumps in the neck.


What is a thyroglossal duct cyst?

-the thyroglossal duct normally disappears but remnants of epithelium may remain and form a thyroglossal duct cyst
-usually near or within the body of the hyoid and forms a swelling on the anterior part of the neck on the midline
-the size is 1-4cm in diameter
-a thyroglossal cyst moves upwards on tongue protrusion
-when they poke their tongue out their skin may be drawn in


What are the majority of metabolic thyroid diseases due to?

- 98% are due to a primary abnormality of the thyroid gland itself
-pituitary failure rarely presents with isolated hypothyroidism
-very rare for a pituitary adenoma to produce TSH and lea to thyrotoxicosis


How can the TSH level be used to screen for hyperthyroidism and hypothyroidism?

- if the TSH is raised, then the thyroid gland is under functioning (hypothyroid)
-if the TSH is low, then the thyroid gland is over functioning (hyperthyroidism)


What is the difference between thyrotoxicosis and hyperthyroidism?

- in hyperthyroidism there is over activity of the thyroid gland and it is the source of the prob;em
-in thyrotoxicosis, the difference is that there is too much thyroid like activity for example by taking thyroxine or hyperthyroidism


what is the TSH and free thyroxine (T4) in thyroid disease?

Hypothyroidism: TSH increased , T4 decreased
Hyperthyroidism : TSH decreased, T4 increased

Normal TSH range 0.5-5.0 mIU/L and normal free T4 range is 10-25 pmol/L however use lab levels


What is a goitre?

- a goitre refers to a thyroid swelling
- they can be diffuse, multinodular or a single nodul


When can a physiological goitre (normal thyroid function) occur?



How does iodine deficiency lead to a goitre?

- reduced thyroxine levels (T4) leads to increased TSH
-this lead to general thyroid enlargement, usually nodular
-severe cases become hypothyroid
-iodine deficienct areas are mainly mountainous areas


Which goitre is most common in the uk?

- multinodular goitre
-affects 5% of western population, 7 x more common in women
-unknown aetiology
-normal thyroid function
-although after many years a very small number may develop hyperthyroidism


What is the problem with retrosternal multinodular goitres?

-a multinodular goitre may enlarge inferiorly into the superior mediastinum to form a Retrosternal goitre and may cause tracheal compression
-this can lead to a respiratory stridor


Name the symptoms of hypothyroidism

-cold intolerance
-weight gain
-low mood, depression
-muscle weakness and cramps
-tiredness and lack of energy
-memory problems and psychosis (myoedema madness)
-swelling of face, hands and feet
-dry flaky skin
-hair loss particularly outer 1/3 eyebrows
-menorrhagia (heavy periods)
-symptoms of CTS due to mucopolysaccharides deposition


Name the signs of hypothyroidism

- weight loss
-coarse brittle hair and dry skin, loss of outer 1/3 eyebrows
-pallor - peaches and cream face
-coarse facial features and periorbital puffiness
-non pitting oedema -myxoedema due to deposition of MPS
-ascites or pericardial effusion - both uncommon


What is myxoedema?

-non pitting oedema
-particularly around he eyes, hands, feet
-term also used to mean hypothyroid in general

Strictly speaking, describes the deposition of mucopolysaccharides but also means hypothyroid.


What are the causes of hypothyroidism?

-autoimmune e.g. Hashimotos disease. Antibodies to thyroglobulin and thyroid peroxidase are present in the blood.

-severe iodine deficiency
- post surgical removal of thyroid with inadequate thyroxine replacement


How can you treat hypothyroid?

-oral thyroxine (not destroyed by gastric acid)
-adjust the dose to normalise serum TSH


What is thyrotoxicosis?

Excessive thyroid hormone in the bloodstream.


What is hyperthyroidism?

-is thyrotoxicosis due to the overproduction of thyroxine by the thyroid gland
-it can be due to excessive intake of endogenous thyroid hormone or due to hyperthyroidism


What are the symptoms of thyrotoxicosis?

-overactive, tiredness,
-intolerance to heat - sweaty hands
-weight loss despite increased appetite
-trembling, shaking
-proximal muscle weakness


What are the signs of thyrotoxicosis?

-weight loss
-sweaty hands
-fine hand tremor
-bounding pulse wide pulse pressure
-proximal myopathy
-lid lag
-staring eyes


Which muscle is responsible for lid lag?

-levator palpebrae superioris muscle
-90% skeletal muscle, 10% smooth muscle
-the smooth muscle portion supplied by the sympathetic nervous system
-over stimulation of SNS leads to 'staring eyes' and lid lag


What are the causes of thyrotoxicosis due to hyperthyroidism?

1. Hyperthyroidism due to Graves' disease
2. Toxic multinodular goitre
3. Toxic adenoma


What is Graves' disease?

-autoimmune disease
-thyroid component caused by a circulating immunoglobulin called thyroid stimulating immunoglobulin (TSI)
-this immunoglobulin attaches to and stimulates the TSH receptor
-this causes all the classical signs and symptoms of thyrotoxicosis however there are additional unique features of Graves' disease


What are the additional unique features of Graves' disease?

-pre tibial myxoedema
The exophthalmos and pre tibial myxoedema are both part of the autoimmune disease
-orange peel appearance on the shins


What is a toxic adenoma?

- a single adenoma which develops in the thyroid gland and produces thyroxine autonomously


What is the treatment for thyrotoxicosis?

- carbimazole - this prevents thyroid peroxidase from coupling and iodinating tyrosine residues on thyroglobulin thereby reducing production of T4
-surgical excision of thyroid (thyroidectomy)
-ablative dose of radioactive iodine