Pharm Chapter 31
Card Set Information
Pharm Chapter 31
Thyroid Parathyroid Hormones
Thyroid and Parathyroid Hormones
What does the Thyroid do?
Promote normal growth and development
What does the parathyroid do?
Regulates Ca++ homeostasis
Maintains normal bone mineralization
What suggests that T4 is a precursor to T3?
T3 may exert most of the physiologic effects on tissues
(conversion occurs in peripheral tissues)
How are thyroid hormones synthesized?
Adding iodine to residues of the aa tyrosine
Add 1 iodine atom= monoiodotyrosine
Add 2 iodine atoms= diiodotyrosine
: monoiodotyrosine + diiodotyrosine
: diiodotyrosine + diiodotyrosine
How are thyroid hormones regulated?
TRH from hypothalamus stimulates release of TSH from ant. pituitary
TSH goes to thyroid gland to stimulate production of T3 and T4
: increase inhibits TSH, prevents high levels of peripheral thyroid hormones
What are some physiologic effects of thyroid hormones?
Can be direct or facilitate other hormones
: ↑ basal metabolic rate and heat production
: stimulates release and enhances effect of GH
: ↑'s HR and myocardial contractility, ↑ing cardiac output
: ↑'s glucose availability and lipids for cellular activity
What is Thyrotoxicosis?
treated w/drugs that attenuate thyroid hormones
Can be cause by tumors and endocrine regulation problems
Enlargement of thyroid or goiter
What is Diffuse toxic goiter?
Type of Hyperthyroidism
Caused by problem of immune system
: Remove thyroid or administer radioactive iodine
What are drugs used to treat Hyperthyroidism?
How do Antithyroid agents work? Examples?
Inhibit thyroid hormone synthesis
Inhibit thyroid peroxidase enzyme
Prevent coupling of residues within thyroglobulin molecule
Block conversion of T4 to T3 (propylthiouracil)
Prophythioracil (Propyl-Thyracil), Methimazole (Tapazole)
How does iodide treat hyperthyroidism?
Large doses cause rapid decrease in thyroid function (temporarily)
Diminishes after 2 weeks
How does radioactive iodide work?
Emits beta radiation to destroy thryoid follicle cells
No damage to surrounding tissue in gland
Permanently ablates thyroid gland
How do beta-adrenergic blockers help hyperthyroidism?
Don't directly decrease hormones
Suppresses symptoms such as tachycardia, palpitations, fever, restlessness
What are types of Hypothyroidism?
Goiter (may be present in some forms of hypothyroidism)
: Lack of dietary iodine (endemic goiter)--->no negative feedback of TSH, so increase in thyroglobulin
What are some thyroid hormones?
Natural and synthetic
Used to treat Hypothyroidism
What is the controlling factor of PTH?
Ca++ in the blood
Decrease in Ca++ activates receptor on cell membrane and increases PTH release
How does PTH release Ca++ into the bloodstream?
Liberates Ca++ from bone--->increases bone turnover
What are the physiologic effects of PTH?
Liberates Ca++ from bone
↑ renal reabsorption of Ca++ and ↑ phosphate excretion
↑ Ca++ absorption from GI tract (increases conversion of Vitamin D to calcitriol which stimulates Ca++ absorption from intestine)
What are the two primary fxns of bone?
1.) Rigid framework
2.) Provides Ca++ pool
How do PTH levels affect bone?
: accelerate bone breakdown (and fracture)
: enhance bone formation (stimulate osteoblastic activity)
What regulates bone homeostasis?
GC's (catabolic effect)
Estrogens, androgens, insulin, thyroid hormone (enhance bone formation)
How does Vitamin D affect bone?
Promotes muscle growth and increase strength and lean body mass
From diet or UV light on skin
↑ supply of Ca++ and PO4 (GI absorption)
What is a PTH antagonist?
Calcitonin (from thyroid gland)
Lowers blood Ca++ by stimulating bone formation and ↑ incorporation of Ca++ into skeletal storage
What happens when Blood Calcium levels are not maintained?
Falls below 6mg/100mL, then titanic muscle contractions ensue
Levels greater than 12mg/mL depresses nervous function
What helps prevent bone loss?
Alone will not prevent osteoporosis but is helpful with other Rx's
Calcium carbonate (Tums)
Calcium citrate (Citracal)
What does Vitamin D do?
Precurosr for cmpds that
↑ intestinal absorption and decreases excretion of Ca++ and PO4
Enhances bone mineralization
Fat soluble, can lead to toxicity
What are bisphosphonates?
Reduce bone resorption by inhibiting osteoclastic activity
Used in Paget disease
Used in neoplastic disease
Can help prevent bone loss associated with prolonged administration of GC's
Primary Rx's for osteoporosis (Improve bone health in women)
How does Calcitonin work?
Decreases blood Ca++ levels and promotes bone mineralization
Used to Rx hypercalcemia and decrease bone resorption in Paget's
Human Calcitonin (Cibalcalcin)
What can help treat postmenopausal osteoporosis?
↑ bone mineral content and reduce risk of fractures
Combined with Ca++ supplements
Synthetic form of PTH
Calcimimetic agent (mimics endogenous Ca++)