Week 4: Thyroid Gland

Thyroid anatomy

anterior lower neck, inferior to larynx, on both sides of trachea

3 lobes of thyroid

right, left, pyramidal

3 tests for thyroid gland

thyroid imagine, ultrasound, fine needle aspiration

thyroid imagine

iv administration of radionuclides allows for better images

ulrasound

assess nodules

fine needle aspiration

assess for neoplasm

thyroid hormones

thyroxine (t4), triiodothyronine (t3), calcitonin, TSH

Thyroxine and triiodothyronine functions

increases metabolic rate of cells and protein synthesis, impacts function of most tissue

t3 and t4 needs ___ to be synthesized

iodine

what causes release of t3 and t4

stimulated by TSH

calcitonin

decreases release of calcium from bone (bone resorption)

steps of negative feedback loop for thyroid

1) stimulus

2)hypothalamus increases secretion of TRH

3)pituitary secretes TSH into circulation

4)Thyroid increases T3 and T4

5)goes to target cells to increase metabolism

6)negative feedback, high levels of t3/4 inhibits secretion of TSH and TRH

Thyroxine Total measures

both T4 bound to tissue and T4 circulating in blood stream

T4 free measures

T4 circulating in bloods tream, is a better measure of thyroid function since this is when its available to work on tissue

hypothyroid disease

increased TSH and Decreased T4

pituitary disease

decreased TSH

types of hyperthyroidism

graves, thyroiditis, thyroid ademona, thyroid carcinoma

types of hypothyroidism

primary hypothyroidism, hashimoto thyroiditis

hyperthyroidism is

excessive sympathomimetic and catabolic activity (tissue are over exposed to thyroid hormones)

what is decreased in hyperthyroidism

vagal tone (parasympethetic), leads to HR variability

what levels are elevated in hyperthyroidism

free t4 and t3

hyperthyroid signs/symptoms

nervousness, insomnia, irritation, emotional lability, tremors, hyperactivity, tachycardia, moist/warm skin, perspiration, heat intolerance, weight loss, increased appetite, hair loss, exophthalmos, reduced menstruation

exophthalmos

bulging/protruding eyes, decreased blinking and eye movements, can lead to optic nerve damage

what causes exophthalmos

from increased sympathetic stimulation

graves disease

familial autoimmine disorder that activates TSH receptors leading to excess t3/t4, most common hyperthyroid case, more in women

main feature of graves

exophthalmos

other features of graves

enlarged thyroid,a fib, fine hand tremors, quad weakness, pretibial myxedema

thyroiditis

inflammation of thyroid gland that causes overproduction of t3/t4

cause of thyroiditis

acute bacterial infection, subacute viral infection, postpartum (somtimes unknown)

thyroid ademonas

benign growth, if larger than 4cm produces excessive thyroid hormones

thyroid carcinomas

cancerous growth of thyroid, most common type of endocrine cancer, more in women

presentation of carcinomas

hard, painless nodules

treatment of carcinomas

removal of all/part of thyroidism (makes they hypothyroidism so they need hormone replacement), highly treatable

med management of hyperthyroidism

antithyroid meds, radioactive iodine, surgery (partial/subtotal thyroidectmoy)

risk of partial/subtotal thyroidectomy

damage to laryngeal nerve, hemorrhage, hypoparathyroidism

with both RAI and surgical removal, they are now

hypothyroid (need supplements)

pt implications for hyperthyroidism

heat intolerance, exercise intolerance, reduced exercise capacity (RPE, vitals, fatigue)

primary hypothyroidism

decreased secretion of thyroid hormone, thyroid doesnt respond fully to TSH

because it doesn't respond to TSH,

not enough t3/4 is produced, hypothalamus senses that and triggers pituitary to release more TSH

when thyroid function is low, TSH levels are

elevated (best indicator of hypothyroidism)

signs/symptoms of hypothyroidism

generalized slow body metabolism, bradycardia, constipation, lethargy, cold intolerance, weight gain with decreased appetite, skin dry and cold, dry hair, decreased perspiration, altered lipid metabolism

hashimoto thyroiditis

autoimmune disorder where it attacks thyroid, causes destruction of thyroid gland resulting in low t3/4 and increased production of TSH

med management of hypothyroidism

correct thyroid deficiency with meds, some on replacement therapy because even if TSH is normal it can still cause symptoms,

why can you not increase dose of thyroid meds for those with hypothyroidism

can cause A fib and osteoporosis

may be relationship between hypothyroidism and

fibromyalgia

PT implications for thyroid disorders

dry/edematous skin (hypo) are prone to tears, older adults on replacement are at risk for bone fractures

chronic decreased metabolic rate leads to

weakness and activity intolerance (so once replacement therapy is started, you need to begin improving activity tolerance)