Thyroid and Parathyroid glands Flashcards
where the thyroid and parathyroid is located
thyroid: paried lobes on larynx
parathyroids: 4 (usually) on thyroid
difference between T3 and T4 produced by thyroid
T3- more active form, made in smaller amounts
T4- converted to T3 in tissues
what controls the secretion of T3 and T4 from the thyroid
TSH (thyroid stimulating hormone) from the pituitary gland
what T3 and T4 thyroid hormones are used for in body
stimulates O2 consumption in cells, regulates fat and carb metabolism, needed for cell growth and maturation, increase nutrient absoption in GI tract
what causes hyperthyroidism
thyroid tumor secreting excessive hormones
signs of hypertyroidism
older cat, hyperactive, weight loss, polyphagia, increased HR, greasy hair coat, alopecia
possible causes of hypothyroidism
lack thyroid hormones (primary): thyroiditis, idopathic atrophy lack TSH from pituitary (secondary): pituitary tumor lack iodine (dietary) produces goiter
signs of hypothyroidism
lethargy, overweight, cold intolerant, dermatitis, alopecia, “tragic expression”
resting T4 tests for
hyperthyroidism, not hypo- many other factors decrease T4 levels
factors besides hypothyroidism that may decrease resting T4 levels
lower w age, certain illnesses, meds (phenobarbital or steroids), certain breeds (german shepards, labs, cockerspaniels, beagles, giant breeds)
what TSh response tests for and how it is done
hypothyroid and differenciate between primary and secondary
take baseline sample (resting T4), inject TSH, take second sample 6 hrs later
TSH response testing in normal animal, primary hypothyroidism, and secondary hypothyroidism
norm- T4 doubles
primary hypo- no change, both low (lack thyroid hormones)
secondary hypo- 2nd sample extremely elevated (we replace TSH that isnt being made by pituitary)
why we may see lipemia in a fasted blood sample of a hypothyroid animal, and high cholesterol
thyroid hormones needed to regulate fat and carb metabolism
_____in thryoid secretes hormones, _____ in thyroid stores them
parafollicular cells secrete, follicles store
what calcium is needed for in body
w/ Ph for bone and teeth, muscle contractions, blood coagulation, nerve impulse transmission, enzymes systems
what Ph is needes for in body
w/ calcium for bone and teeth, nucleic acids, cell metabolism
2 hormones responsible for balance of Ca:P ratio and how they work, and where they are made
Calcitonin- produced by thyroid C-cells/ intrafollicular cells; decreases blood calcium, stores in bone
Parathormone- from parathyroid chief cells, increases blood calcium
where parathormone acts on to increase blood calcium
breaks down bone, acts on kidneys so more Ca will be absorbed and more Ph excreted, acts on intestine receptors so more Ca will be absorbed
diseases that affect Ca:Ph ratio (primary and secondary)
hyperparathyroidism: increases blood Ca
primary: parathyroid tumor (rare)
secondary: something exerting action on parathyroid- kidney disease (Ca excreted, PT hormone increases), nutritional, pseudohyperparathyroidism
most common reason for Ca:Ph ratio imbalance
nutritional secondary hyperparathyroidism
causes of nutritional secondary hyperparathyroidism
dietary Ca too low, dietary Ph too high, inadequate vitamin D
how vitamin D is made from UVB light
inactive form cholecalciferol is made, actived in liver
signs of nutritional secondary hyperparathyroidism
thin bones, fracture easily (osteoporosis), loose teeth, can cause ricketts in young
what causes rickets in young
insufficient vitamin D or Ca
pseudohyperparathroidism is also called
hypercalcemia of malignancy
what is pseudohyperparathroidism
tumor (mammary, lymphosarcoma, or perianal) produces PTH- like substance (parathyroid hormone), Ca pulled from bones, see mineralization/calcium deposits in soft tissue (kidney, liver, heart)
an inactive parathyroid is associated w what in diary cattle around parturition
milk fever/ parturient paresis
sample we use to test Ca:ph levels
serum or heparinized plasma (not EDTA or oxylate bc contain Ca)
