Thyroid Disorders Flashcards
Where is the thyroid gland located?
Anterior neck C5-T1
Below the laryngeal prominence (adams apple)
superior to cricoid cartilage
Describe the shape of the thyroid gland and blood supply
Butterfly shape 2 lobes- connected in the middle by the isthmus
Superior and inferior thyroid arteries
Superior middle and inferior thyroid veins
Sympathetic innervation
What is the function of thyroid hormones?
Metabolic regulation..
incr. rate of
lipogenesis and thermogenesis
gluconeogenesis and glycogenolysis
basal metabolic rate
proteinsynthesis
cardiac output
bone resorption
Which is the more abundant and active form of thyroid hormones?
T4 more abundant
T3 active
T4-> T3 at peripheries
How do thyroid hormones travel in circulation?
Protein bound as fat soluble
Albumin and thryonine binding globulin
Thyroid hormones belong to which axis?
Hypothalamic- pituritary - thyroid axis
What is the difference between hyperthyroidism and thyrotoxicosis?
Hyperthyroidism= overactive thyroid gland
Thyrotoxicosis = excessive thryoid hormone in circulation - may be from incorrect thyroid medication than hyperthyroidism
What is hyperthyroidism?
Overproduction of thyroid hormone due to thyroid gland over activity
What is primary hyperthyroidism
Over production of thyroid hormones due to abnormal overactivity of the thyroid gland - thyroid pathology
What is secondary hyperthyroidism?
Over production of thyroid hormones due to over-stimulation of the thyroid gland from TSH
Pathology of hypothalamus or pituitary
Describe the epidemiology of hyperthyroidisim?
Women > men
20-40yrs presentation
2.5% women
What are the general signs and symptoms for hyperthyroidism?
Symptoms…
- Wt loss, anxiety/ irritability, heat intolerance (hot and sweaty)
- hyperphagia, menstrual disturbances, palpitations
Signs
Tachycardia, tremor, thin hair, hair loss, goitre
What are the general signs and symptoms for hyperthyroidism?
Symptoms…
- Wt loss, anxiety/ irritability, heat intolerance (hot and sweaty)
- hyperphagia, menstrual disturbances, palpitations
Signs
Tachycardia, tremor, thin hair, hair loss, goitre
What are the Graves specific signs for hyperthyroidism?
Diffuse (smooth) goitre
Grave’s eye disease- exophthalmos- buldging eye due to extraoccular muscle inflam
Pretibital myxoedema- purple/ red symmetrical lesions on anterolater shin
Describe the pathophysiology for Grave’s disease
- Autoimmune condition- IgG serum antibodies
- TSH receptor antibodies (TRAb) mimic TSH and bind to TSH receptor on thyroid gland
- Increasing thyroid gland stimulation for excess thyroid hormone production
- causing smooth goitre, thyroid cell hyperplasia and hyperthryoidism
Describe the aeitology for hyperthyroidism
Graves disease (2/3rd cases)
Toxic multinodular goitre
Toxic adenoma
Drug induced - amiodarone
What are the risk factors for hyperthyroidism?
Smoking
Women
HLA - DR3
Amiodarone
What is the first line drug therapy for hyperthyroidism, action and 2 side effects?
Carbimazole - prevents T4 syntheis
Hypothyroidism and agranulocytosis
What are the 2 regimes for carbimazole?
Hyperthyriosism
Block and replace- thyroxine and and carbimaole
Titration
What is the second line drug therapy for hyperthyroidism and its action?
Propylthiourcil, prevents the conversion of t4->t3
What drug can be given to target thesymptoms of hyperthyroidism?
Non-specifc beta blockers eg pronanolol
decr. sympathetic ns activation
Despite drug therapy, what are the other treatments for hyperthyroidism?
Radioiodine (CI pregnancy and breastfeeding)
Thyroidectomy - partial
What is the class of drugs and action for hyperthyroidism
Thionamides - prevent thyroid hormone synthesis
What are the complications of hyperthyroidism?
AF, osteoporosis (thyroid hormones increase bone resorption osteroclast activity incr)
What is thyroid crisis?
Rapid deterioration of thyrotoxicosis so big increase in T4
What are the signs of thyroid crisis?
Hyperpyrexia
Tachycardia
Delerium, coma and death
What is the treatment of thyroid storm
Large dose of carbimazole
propanolol
KI (blocks uptake of iodine into thyroid gland)
What are the 3 causes of excess thyroid hormones?
Gland hyperfunction
Leakage of preformed hormones
Ingested thyroid hromones
What are the investigations and results for hyperthyroidism?
Thyroid function test
- Primary = low TSH, high t3/3
- Secondary = high TSH, t3/4
Thyroid antibodies
- TRAb = graves specific
- TPO = all cases
What is the most common endocrine disorder?
hypothyroidism
What is hypothyroidism?
Deficiency of thyroid hormones due to reduced production from the thyroid gland
What is the difference between primary and secondary (central) hypothyroidism?
Primary is reduced thyroid hormone production due to disorder of the thyroid gland - Raised TSH, low t3/4
Secondary is reduced thyroid hormone production due to disorder or pathology of the pituitary gland or hypothalamus- low TSH, t3/4
Describe the epidemiology of hypothyroidism
More common in womem
2-5% prevelance
primary <95% cases
What are the causes of primary hypothyroidism?
- Iodine deficiency
- Hashimoto’s thyroiditis (common in developed countries)
- Drugs- antithyroid, amiodarone, lithium
- Thyroidectomy
What are the causes of secondary hypothyroidism?
Hypopituitarism
Pit tumour
Surgery
Drugs eg cocaine
What are the investigations for hypothyroidism?
- TFT:
P. High TSH, low T3/4
S. Low TSH, low T3/4 - Thyroid antibodies
TPOAb - hashimotos specific - Hyperlipidaemia and hypernatraemia
What is the managment for hypothyroidism?
Levothyroxine (T4)
- Life-long
- P. titrated for TSH levels to normalise
What are the complications of hypothyroidism?
- coronary heart disease and stroke
- dyslipidaemia
- p. Incr. risk infertility and miscarriage
What are the signs of hypothyroidism?
Bradycardia
Reduced reflexes reaction
Ataxia
Dry, thin skin and hair
Yawning/ coma
Cold hand and low temp
Ascites
Round puffy face
Defeated demeanour
Immobile and ileus
Congestive
What are the symptoms for hypothyroidism?
Wt gain
Cold intolerance
Fatigue
Low mood
Hoarse voice
Muscle cramps and myalgia
Poor memory
What are the risk factors for hypothyroidism?
- Fam/ personal history of autoimmune diseases eg addisons, coeliac, vitiligo, t1dm
-thyroidectomy - history iodine def
What are the 5 types of thyroid malignancies?
Papillary
Follicular
Medullary
Lymphoma
Anaplastic
What is the clinical presentation of thyroid malignancies?
Dysphagia
Hoarse voise
Nodules; hard, irregular, incr. size`
What is the treatment for thyrid malignancies?
radioactive iodine
surgery
thyroxine
What is the differential diagnosis of thyroid malignancy
Goitre
What is Hashimotos thyroiditis?
- Autoimmune condition that can cause hypothyroidism
- anti-TPO antibodies and anti-thyroglobulin antibodies cause thyroid inflam.
- causes goitre then gland atrophy
How may amiodarone cause hypothyroidism?
It prevents t4 -> t3 in peripheries
It has cytotoxic effects on thyroid follicular cells
How may amiodarone cause hyperthyroidism?
High iodine content can cause unregulated thyroid hormone production
