Hyperthyroidism and Hypothyroidism Flashcards
What are the definitions of hyperthyroidism, hypothyroidism and thyroiditis?
Hyperthyroidism = overactive thyroid Hypothyroidism = underactive thyroid Thyroiditis = inflammation of the thyroid caused by excess thyroid hormone
What is the difference between primary and secondary thyroid disease?
Primary - disease affecting the thyroid gland itself
Secondary - hypothalamic or pituitary disease affecting the thyroid
What are the thyroid hormones?
T3 (triiodothyronine)
T4 (thyroxine)
Is more of T3 or T4 secreted?
T4 (80%)
Describe the hypothalamic-pituitary-thyroid axis?
The hypothalamus secretes TRH (thyrotropin releasing hormone)
TRH stimulates the pituitary to secrete TSH (thyroid stimulating hormone), also called thyrotropin
TSH stimulates the thyroid to secrete T3 and T4
Excess T3 and T4 inhibit the pituitary gland and hypothalamus to stop secreting TSH and TRH
Which thyroid hormone needs to undergo an extra step, and what is that step?
T4 is converted to T3 which activates it
How are TSH levels affected in primary hyper and hypothyroidism, and why?
In primary hyperthyroidism the problem in the thyroid means too much T3 and T4 are secreted so the negative feedback effect means TSH levels are low
In primary hyperthyroidism the problem in the thyroid means not enough T3 and T4 are secreted so the negative feedback effect means TSH levels are high
What are the symptoms of thyrotoxicosis?
Brittle, thin hair Proptosis (bulging eyes) Enlarged thyroid Palpitations Tremor of fingers Soft nails Sweating Frequent, loose bowel movements Infertility Scant menstrual periods Muscle weakness Heat intolerance Weight loss Anxiety, nervousness, irritability Insomnia
What are the causes of thyrotoxicosis?
Graves' disease Hashitoxicosis Thyrotropinoma Thyroid cancer Toxic solitary thyroid nodule Toxic multi nodular goitre Thyroid inflammation (subacute, post-partum or drug-induced thyroiditis) Over-treatment with levothyroxine Metastatic thyroid carcinoma
Which causes of thyrotoxicosis are associated with hyperthyroidism?
Grave's disease Hashitoxicosis Thyrotropinoma Thyroid cancer Toxic solitary thyroid nodule Toxic multi nodular goitre
What percent of the population are affected by Graves’ disease?
Females - about 1%
Males - about 0.1%
What ages usually present with Graves’ disease?
20-50 year olds
What causes Graves’ disease?
Autoimmune - interacting susceptibility genes (70%) and environmental factors
What is the biggest risk factor for developing Graves’ disease?
Smoking
What are the results of blood tests done in Grave’s disease?
TSH - low Free T3/4 - high Hyperhalcaemia Increased alkaline phosphatase Leucopenia
What conditions are associated with Graves’ disease?
Osteoporosis
What antibody test results indicate Graves’ disease?
TSH receptor antibody (70-100%)
Anti-TPO antibody (70-80%)
What clinical signs are specific to Graves’ disease?
Pretibial myxoedema
Thyroid acropachy (clubbing)
Thyroid bruit
Graves’ eye disease
What is nodular thyroid disease?
Hyperthyroidism with a nodular-feeling asymmetrical goitre
Occurs in older patients with a more insidious onset
What will blood test results be in nodular thyroid disease?
High free T4 and T3
Low TSH
Antibody negative
High uptake on scintigraphy
What investigation is diagnostic for nodular thyroid disease?
Thyroid ultrasound
What is thyroid storm (crisis)?
Severe hyperthyroidism involving respiratory and cardiac collapse, hypothermia, exaggerated reflexes - a medical emergency
Which patients are most likely to have thyroid storm?
Hyperthyroid patients with an acute infection/illness or recent thyroid surgery
What is the treatment for thyroid storm?
Lugol’s iodine
Glucosorticoids
Propylthiouracil
Beta blockers
What is the first line treatment for hyperthyroidism?
Carbamizole
What are the contraindications of carbamizole?
Not used in early pregnancy
What is the second line treatment for hyperthyroidism, and when is it given?
Propylthiouracil
In the 1st trimester of pregnancy or young women who could get pregnant
What is the mechanism of anti-thyroid drugs?
Inhibition of thyroid peroxidase, to block thyroid hormone synthesis
What are the side effects of anti-thyroid drugs?
Allergic reeaction
homeostatic jaundice
Agranulocytosis
What are the symptoms of agranulocytosis?
Fever
Oral ulcer
Oropharyngeal infection
What is done if a patient exhibits symptoms of agranulocytosis?
Stop drugs immediately and urgent FBCcheck
ATDs cannot be used again
When are beta blockers used in hyperthyroidism?
To manage symptoms of sympathetic activity like palpitations
When are beta blockers not used, and what is used instead?
In asthmatic patients
CCBs used instead
When is radioiodine used in hyperthyroidism?
1st choice for relapsed Graves’ disease and nodular thyroid disease
When is radioiodine contraindicated?
Pregnancy
Thyroid eye disease (but can be used with steroid cover_
What are the risks of thyroidectomy?
Recurrent laryngeal nerve palsy
Hypothyroidism
Hypoparathyroidism
What are causes of thyroiditis?
Hashimoto's thyroiditis De Quervain's (viral) Post-partum Drug-induced Radiation Acute supportive thyroiditis
What is subacute thyroiditis?
Usually self-limiting, may be triggered by a viral infection
May be associated with neck tenderness, fever or other viral symptoms
What is subclinical thyroid disease?
Abnormal TSH with normal thyroid hormone levels
Can progress to overt thyroid disease
Treatment advised if borderline overt
What is sick euthyroid syndrome?
The hypothalamic-pituitary-thyroid axis is affected by intercurrent illness
What are the goitrous causes of primary hypothyroidism?
Hashimoto's thyroiditis Iodine deficiency Drug-induced (amiodarone, lithium) Maternally transmitted (e.g. antithyroid drugs) Hereditary biosynthetic defects
What are the non-goitrous causes of primary hypothyroidism?
Atrophic thyroiditis
Post-ablative therapy
Post-radiotherapy
Congenital development defect
What is the most common cause of hypothyroidism?
Hashimoto’s thyroiditis
What is Hashimoto’s thyroiditis?
Autoimmune destruction of the thyroid gland and reduced hormone production
What investigative signs are characteristic of Hashimoto’s thyroiditis?
Antibodies against thyroid peroxidase (TPO)
T-cell infiltrate and inflammation microscopically
What are the clinical features of Hashimoto’s thyroiditis?
Coarse, sparse hair Puffy face Vitiligo Cold intolerance Pitting oedema Reduced heart rate Decreased appetite Weight gain Constipation Hoarse voice Obstructive sleep apnoea Depression Muscle stiffness Peripheral neuropathy Carpal tunnel syndrome Heavy periods
What will the results of blood tests be in Hashimoto’s thyroiditis?
High TSH Low free T3/4 High MCV High creative kinase High LDL cholesterol
What antibodies are positive in Hashimoto’s thyroiditis?
Anti-TPO antibody
Anti-thyroglobin antibody
What is the management for Hashimoto’s thyroiditis?
Levothyroxine
What are the contraindications for levothyroxine, and what effects do they have?
PPIs
Iron tablets
Calcium tablets
Impair absorption so levothyroxine doesn’t work
What is myxoedema coma?
An extreme case of hypothyroidism that can involve bradycardia, heart block and type 2 respiratory failure
Which patients are typically affected by myxoedema coma?
Elderly women with long-standing but frequently unrecognised or untreated hypothyroidism
What is the treatment for myxoedema coma?
Cardiac monitoring for arrhythmias
Broad spectrum antibiotics
Thyroxine - give cautiously and add hydrocortisone if any indication of adrenal failure
