Thyroid Disorders Flashcards
(21 cards)
What is meant by thyroid disorders?
Medical conditions affecting structure & function of thyroid gland
- remember thyroid hormones role in regulating metabolism
Thyroid disorders are classified based on:
-
Functional status
○ Hypothyroidism - underactive thyroid
gland
○ Hyperthyroidism - overactive thyroid
gland
Euthyroid - normal thyroid function, structural abnormalities may be present:
-
Structural abnormalities
○ Goiter (enlargement of thyroid)
○ Thyroid nodules
○ Thyroiditis
○ Tumours
4 types of causes of Hypothyroidism
-
Primary - due to thyroid
- Hashimoto’s thyroiditis
- Iodine deficiency
- Congenital disorders -
Secondary - due to pituitary
- Trauma
- Tumour -
Tertiary - due to hypothalamus
- Trauma
- Tumour -
Iatrogenic
- Surgical removal of thyroid gland
- Drugs (e.g. lithium, amiodarone)
4 types of causes of Hyperthyroidism
-
Primary - due to thyroid
- Graves’ disease
- Toxic multinodular goiter
- Toxic adenoma -
Secondary - due to pituitary
- TSH secreting pituitary adenoma -
Tertiary - due to hypothalamus
- Tumour #rare -
Iatrogenic
- Drugs (e.g. levothyroxine, amiodarone)
Autoimmune thyroid disorders
Hashimoto’s thyroiditis
Autoimmune destruction → hypothyroidism
Graves’ disease
Autoimmune stimulation of thyroid → hyperthyroidism
What is hypothyroidism?
Medical condition resulting from insufficient production / action of thyroid hormones
- leads to general slowing of metabolic processes
Pathogenesis of Hypothyroidism
- depending on whether primary, secondary, or tertiary
Primary cause: thyroid gland dysfunction
- Hashimoto’s thyroiditis: destruction of thyroid tissue by auto-antibodies (e.g. anti-TPO, anti-Tg)
Secondary cause: pituitary failure
no TSH → ↓thyroid stimulation
Tertiary cause: hypothalamic failure
↓TRH = ↓TSH = ↓thyroid hormones
Pathogenesis Hashimoto’s thyroiditis
Immune system attack thyroid tissue → target thyroid auto-antigens (e.g. Tg, TPO) → T helper cells activate B cells → anti-Tg, anti-TPO antibodies produced
- Tg - Thyroglobulin
- TPO - Thyroid peroxidase
Clinical features of hypothyroidism
Symptoms
- fatigue
- cold intolerance
- weight gain, puffiness
- dry, coarse skin
- hair thinning / loss
- constipation
- menstrual irregularities
- low mood, depression
- slow reflexes brain fog
Signs
- bradycardia
- reduced body temperature
Investigations for hypothyroidism
1. Thyroid function tests
- TSH: high in primary hypothyroidism
- Free T4: low
- Free T3: may be normal or low
2. Auto-antibodies
- anti-thyroid peroxidase (anti-TPO) antibodies
- anti-thyroglobulin antibodies
both present in Hashimoto’s thyroiditis
3. Imaging
- Thyroid ultrasound: may show heterogeneous gland in Hashimoto’s
- MRI brain: if suspect secondary/tertiary hypothyroidism
- Others (if needed)
FBC: may show anaemia
Serum sodium: may be low (hyponatremia)
What is hyperthyroidism?
Medical condition where thyroid gland produces excessive thyroid hormones
- leads to increased metabolic rate & heightened sympathetic nervous activity
Pathogenesis of Hyperthyroidism
Pathogenesis: Graves’ disease
Autoimmune response against TSH receptor → TSH antibodies formed → unregulated stimulation of thyroid gland
Clinical features of hyperthyroidism
Symptoms
- shakiness, anxiety
- heat intolerance
- palpitations, shortness of breath
- weight loss
- increased bowel frequency
- light menstrual periods
Signs
- tachycardia
- tremor
- warm, sweaty hands
Investigations for hyperthyroidism
1. Thyroid function tests
- Serum TSH: low
- Free T3 & Free T4: high
2. Auto-antibodies
- TSH antibodies: present in Graves’
3. Imaging
- Radioactive iodine uptake scan: increased uptake in Graves’
- Thyroid ultrasound: may show increased vascularity in Graves’
What are thyroid nodules?
Abnormal growths (lumps) in thyroid gland
- nearly always benign
- very common in older women
Causes of thyroid enlargement (goiter) can be either …… or ……
Benign
Malignant
Benign causes of thyroid enlargement can be either ….. or …..
→ Diffuse
(whole gland uniformly enlarged)
Examples: Hashimoto’s thyroiditis
Graves’ disease
Infections
→ Nodular
(with localised swellings or nodules)
Examples: Thyroid adenoma
Toxic multinodular goiter
True / False
Malignant causes of thyroid enlargement are usually nodular.
True.
- 4 main types
4 main types of malignant nodular thyroid enlargement
- Papillary carcinoma ( > 85%)
- Follicular carcinoma
- Medullary carcinoma
- Anaplastic carcinoma
Investigations for thyroid enlargement
- history
- physical exam (size of mass, lymph nodes)
Labs
- TSH
- Free T3 & T4
- Anti-TPO antibodies
- Thyroglobulin
Imaging
- Neck ultrasound (first-line imaging!)
- Radioactive iodine uptake scan (if TSH low)
Fine-needle Aspiration Biopsy !
if nodules > 1 cm with suspicious features on ultrasound
