Thyroid and osteoporosis Flashcards
Levothyroxine sodium (Synthroid)
- T4 produces normal levels of T3 and T4
- DOC for hypothyroidism
- Drugs levels must be carefully titrated to the individual (TSH levels; Patient S&S)
Liothyronine sodium (Cytomel)
- T3; short half life and duration of action
- Used for initial therapy (rapid levels) but not maintenance
- Many drug interactions
- Side effects similar to hyperthyroidism (reduce dosage or stop for a few days and resume at a lower dose)
Treatment for hyperthyroidism
- Remove the gland by surgery
- Destroy the gland by 131 iodine
- Decrease T4 and T3 by thioamides, iodide
- Block the symptoms by beta blockers
Thioamides-Propylthiouracil (PTU) and Methimazole (Tapazole) MOA
- Decreases synthesis and release of T4
- Methimazole more potent
- PTU–>blocks conversion of T4 to T3
- Effects are gradual (use beta blockers)
- Circulating T3/T4 lasts a week or so**
Thioamides indications/therapeutic effects
- First line of treatment for Graves’ (DOC)**
- Used in conjunction with other treatments
- Reduces thyroid storm risk
Thioamides adverse effects
- Black box warning for PTU** (severe liver injury, acute liver failure)
- Methimazole DOC in most cases (unless there are allergies and early pregnancy**)
- Itching and skin rash**
- Granulocytopenia and agranulocytosis** (reversible, watch for sore throat, do blood test)
- Goiter**-may need to add T4 to reduce TSH levels
- Keep dose low in pregnancy (prevent cretinism and goiter in fetus)
Iodide MOA
- Iodide rapidly decreases synthesis and release of T4/T3
- Short term effect (2-8 weeks)
Iodide indications/therapeutic effects
- Decreases vascularity** and thyroid content of gland
- Used for 7-10 days before surgery (can decrease likelihood of thyroid storm)
- Can use in radioactive emergencies**
Radioactive iodide-131 I MOA
- 131 iodide taken into the gland specifically
- Small amounts (micro)=diagnostic
- Large amounts (milli)=destroys gland
Radioactive iodide indications/therapeutic effects
-Used in elderly patients and those w/heart disease
Radioactive iodide adverse effects
- usually cause hypothyroidism over time
- Thyroid storm risk-decrease risk by use of thioamide (not iodide!) prior to treatment
Propanolol (inderal) MOA
- Beta blocker: decreases many of the S&S of hyperthyroidism
- Propanolol specifically inhibits the peripheral conversion of T4 to T3
Propanolol indications/therapeutic effects
-Used to prepare for surgery and while waiting for thioamides or radioactive iodide to take effect
Propanolol contraindications/precautions
asthma
Calcitonin (Miacalcin)
- Decreases bone resorption of calcium**
- Antagonizes parathyroid hormone**
- Decreases bone pain and loss
- Increases bone density
- Decreases osteoporotic fractures
Calcitonin (Miacalcin) indications
- Osteoporosis (not 1st line)
- Paget’s disease
Calcitonin Pharmacokinetics
- Nasal spray
- Injection
Calcitonin adverse effects
- May cause allergic reactions
- Nasal rhinitis/sinusitis*–>nasal spray
- Nausea and vomiting*–>injection
Teriparatide (Forteo)
- Recombinant parathyroid hormone**
- PTH stimulates remodeling, causing resorption and new bone formation
- Intermittent administration produces bone GROWTH** (only anabolic drug for osteoporosis)
- Actions diminish w/time use antiresorptive agent after 18-24 months
Teriparatide indications
- Treatment for osteoporosis
- Hypoparathyroidism
Teriparatide pharmacokinetics
-Subcutaneous injection (intermittent-once or twice daily)
Teriparatide adverse effects
- Hypercalcemia and hypercalciuria
- Injection site reactions
- Dizziness, leg cramps
Teriparatide contraindications/precautions
- Osteosarcoma (black label warning)**
- Be careful in patients susceptible to any osteosarcoma (pager’s disease, radiation therapy, open epiphyses, hx)
Denosumab (prolia)
- Antibody against receptor activator of nuclear factor kappa-beta ligand (RANKL)
- New treatment for osteoporosis
(DEN=density, OS=osteo, U= human, MAB=monoclonal antibody)
Denosumab MOA
- Inhibits bone resorption
- Antibody to RANK-Ligand, the factor made by osteoblasts that is necessary for the formation of mature osteoclasts **
Denosumab indications/therapeutic effects
- Osteoporosis in men and postmenopausal women at high risk for fractures**
- Increases bone mass and strength in both cortical and trabecular bone**
Denosumab pharmacokinetics
S.C. injection, once/6 months
Denosumab adverse effects
- Hypocalcemia
- Cellulitis, eczema
- Osteonecrosis of the jaw* in cancer studies
Denosumab ABSOLUTE contraindications/precautions
- Hypocalcemia* (fix first)
- Pregnancy-Cat X
Denosumab RELATIVE contraindications/precautions
- Chronic kidney disease
- Patients at risk for serious infections (RANK-RANKL signaling in lymphocytes)
Bisphosphanates (FDA approved=Alendronate [Fosamax], Risedronate [Actonel], Ibandronate [boniva], zoledronic acid [zometa])
(Off label use=Etidronate [didronel], pamidronate [aredia])
- P-C-P bond analogs of pyrophosphate
- Substitutes for PO4 in calcium binding** (incorporates into bone, inhibits bone resorption)
- Powerful drugs
- May not be needed for patients w/osteopenia?
- Long term effects still unknown
Bisphosphanates MOA
- Inhibits osteoclast activity and bone resorption
- Bisphosphanates actually strengthen bone
- Mechanism still unclear
Bisphosphanates indications
- First line of treatment (DOC) for post-menopausal osteoporosis**
- Paget’s disease
Bisphosphanates pharmacokinetics
- Oral preparations: absorption is very poor**
- MUST be taken on an empty stomach** (1/2 glass water; stay upright for 30 min after taking it to decrease esophageal irritation)
- Others are IV injection only
- Given anywhere from once/day to once/year
Bisphosphanates adverse effects-oral
-Abdominal pain, upper GI irritation, esophageal ulceration, constipation, diarrhea, and flatulence
Bisphosphanates adverse effects-IV
-Renal toxicity if given too fast
Bisphosphanates adverse effects-all
- Nausea vomiting**
- May cause a mild hypocalcemia
- Possible atrial fibrillation
- Increased incidence of osteonecrosis of the jaw** after major dental work
