Chapter 6 Endocrine Flashcards
Where is the Thyroid gland located?
Wraps around trachea, just below thyroid cartilage
What is the function of thyroid gland?
Produces thyroid hormones (T3 and T4)
What is T4?
- Thyroxine
- Most abundant thyroid hormones but largely inactive
- less metabolic effect
where is T4 activate to T3?
tissues and liver
What is T3?
- Triidothyroxine
- Active form, greater metabolic effect
What is the tissue in the body that only uses iodine?
Thyroid Gland
How many Iodines does T4 and T3 have?
- T4 = 4 iodine 2 tyrosine amino acids
- T3 = 3 iodine 2 tyrosine amino acids
What feedback does thyroid gland regulate to?
Negative feedback
What does hypothalamus release?
Thyrotropin releasing hormone (TRH)
what does release of TRH causes?
causes the anterior pituitary to release TSH
What does Thyroid stimulating hormone (TSH) do?
Causes thyroid to produce and secrete Thyroxin (T4)
Who/what releases TSH?
Anterior pituitary gland
Activated T3 acts on what? and causes what?
Activated T3 acts on cells to increase metabolism
what causes the hypothalamus to stop releasing TRH?
When there is an increased levels of thyroid hormones
Explain the regulation of the thyroid gland (Negative feedback)
- Hypothalamus releases TRH which causes the anterior pituitary to release TSH
- TSH causes thyroid to release T4
- Activated T3 acts on cells to increase metabolism
- Increased levels of thyroid hormones cause hypothalamus to stop releasing TRH
TSH is used as a marker for what?
TSH is easiest to measure, and used as a marker for thyroid function
Continuum of Thyroid dysfunction (Hyper to Hypo)
-Hyper- Thyrotoxicosis Hyperthyroidism Euthyroid Hypothyroidism Myxedema coma -Hypo-
What is goitre?
An enlargement of thyroid gland
What is nodule
A localized growth of thyroid gland
Is goitre result from hyper or hypo thyroidism?
- Both
- Thyroid cells are stimulated to grow, which may result in hyper or hypo
What causes goitre? (3)
- Elevated levels of TSH ( endemic goitre)
- Toxic goitre (thyroid grows without TSH stimulation tumour)
- Goitrogen drugs
What causes elevated TSH ( endemic goitre)?
- Iodine Deficiency
- Thyroid needs iodine to make T4 and without it the T4 level drops. The Hypothalamus will sense that there is low T4 and will release TRH to try to stimulate the anterior pituitary gland. Anterior pituitary then releases TSH and will continue to release it in order to try to get more T4.
- too much TSH is the result
What causes toxic goitres?
- Benign tumours in the thyroid gland causing the gland to grow uniformly or through nodules
- Thyroid grows without TSH stimulations
How do goitrogen drugs cause goitre?
They interfere with gland uptake of iodine and can cause low levels of T4 which results in elevated TSH and eventually form goitre.
Goitrogen drugs (4)
- Sulphonamides
- Salicylates
- Lithium
- Amiodarone
Does goitre indicates whats going on with thyroid glands?
- NO
- Needs further assessment
how do we identify if the thyroid nodule is benign or cancerous?
Biopsy of tissue is taken
2 types of thyroid nodules
- Functional nodules ( caused by increase TSH)
- Benigh tumours
What is the risk factor of thyroid cancer? and how do we prevents it?
- Radiation is risk factor
- Thyroid is really sensitive to radiation therefore, we have to wear vest with collar on neck to protect thyroid glands.
What is thyroiditis?
Thyroiditis is an inflammation of the thyroid gland
what causes thyroiditis? (4)
- Autoimmune - can lead to hypothyroidism (hashimoto’s thyroiditis)
- Viral infection
- Bacterial infection
- Postpartum thyroiditis
Which of the causes of thyroiditis can people usually recover from?
- Viral infection
- Bacterial infection
- Postpartum thyroiditis
What is Hashimoto’s thyroiditis
- Thyroid tissues is replaced by fibrous functional tissues
- Permanently changed and can no longer or barely make any thyroid hormones
What is Hyperthyroidism
Higher than normal levels of thyroid hormone circulating in blood
What is thyrotoxicosis
A group of symptoms caused by excess levels of thyroid hormone (hyper-metabolism)
What causes Hyperthyroidism (5)
- Auto-immune (Graves disease)
- Toxic nodular goitres/ Thyroid cancer
- Pituitary tumours
- Thyroiditis
- Exogenous iodine ( treatment for endemic goitre)
What is Graves Disease? How does it cause hyperthyroidism?
- Auto-immune
- Antibody mimics TSH and it binds to the TSH receptors causing the thyroid to produce large amount of thyroid hormones
Graves disease is characterized by?
Remission and exacerbations, with or without treatment
How does toxic nodular goitre/ thyroid cancer cause hyperthyroidism?
Nodule or lump grows on the thyroid gland causing it to become enlarged and produce excess thyroid hormones.
- this is independent of TSH
How does pituitary tumours cause hyperthyroidism?
Nodule or lump grows on the pituitary causing it to produce excess TSH which stimulates the thyroid to create more T4 hormones.
How does thyroiditis cause hyperthyroidism?
Thyroiditis can cause excess production of hormones.
how does exogenous iodine cause hyperthyroidism
- Too large of dose can increase excess production of hormones.
- More iodine available to make T4
Clinical manifestations of Hyperthyroidism - CNS (7)
Anxiety, very alert, nervous, depression, insomnia, irritable, heat intolerance
Clinical manifestations of Hyperthyroidism - CVS (6)
- increase CO
- Increase HR
- Afib
- SVT (supra ventricular tachycardia)
- PVCs ( premature ventricular contractions)
- Cardiac hypertrophy
What does fast metabolism do in sympathetic system?
- SNS is sensitive to fast metabolism
Clinical manifestations of Hyperthyroidism - respiratory (2)
- Tachypnea
- Eventually muscle wasting can cause dyspnea
Clinical manifestations of Hyperthyroidism - GI (4)
- increase appetite
- weight loss
- increase BS (bowel sounds)
- Diarrhea
Clinical manifestations of Hyperthyroidism - musculoskeletal (3)
- fatigue
- muscle weakness
- osteoporosis ( rapid bone reabsorption)
Clinical manifestations of Hyperthyroidism - others (2)
- exophthalmos - autoimmune
- Goitre - due to high TSH
What is exophthalmos?
Autoimmune attack which affects soft tissue behind eyes causes inflammation and edema which pushes the eyes forward
-> risk of injury due to eyelids cannot protect bulging eyes
What is the complication of Hyperthyroidism?
Thyroid Crisis ( Thyroid Storm)
When is thyroid crisis most likely to occur?
Most likely to happen in chronic or untreated hyperthyroidism
What is Thyroid Crisis
- It is a rare complication where hyperthyroidism symptoms are intensified
Thyroid Crisis is triggered by? (3)
- illness
- Trauma
- Surgery
Thyroid Crisis is characterized by (14)
- Severe tachycardia
- heart failure
- shock
- fever
- agitation
- delirium
- nausea
- vomiting
- diarrhea
- hyperthermia
- restlessness
- seizure
- abdominal pain
- coma
During thyroid crisis, why is the heart and nerve more sensitive to SNS?
due to more binding sites for epinephrine and norepinephrine are present
What is the treatment for Thyroid Crisis?
Thyroid levels must be reduced and other symptoms managed with medical therapy
Does thyroid Crisis requite immediate medical treatment?
yes