Osteoporosis (Week 5--Pregler) Flashcards
Osteoporosis
Low bone mass, microarchitectural deterioration of bone tissue
Resorption exceeds bone formation but ratio of mineral to matrix remains normal
Risk factors: caucasian or Asian, female, advanced age, hx fracture in first deg relative, low BMI, early menopause, long premenopausal amenorrhea (can be caused by pregnancy/breast feeding), cigarette smoking, alcoholism, low Ca2+ intake, inactive lifestyle
Over 8 million women and 2 million men in US have osteoporosis
Facts about osteoporosis
Over 1/2 all women in US will have osteoporotic fracture in their lifetime
If over 50 and break hip, 24% mortality within a year and 1/3 must go to nursing homes
Osteoblasts
Lay down bone matrix
Osteoclasts
Resorb bone, form lacune
Two types of bone
1) Trabecular: axial, more active metabolically, first site of osteoporosis
2) Cortical: peripheral
What regulates bone formation and remodeling?
Estrogens/androgens
Vitamin D
Parathyroid hormone (PTH)
Local growth factors
Steroid hormones
Thyroid hormones
Illnesses: hematologic disorders, rheumatoid arthritis, Type 1 DM, inherited disorders
Drugs interfere w/bone formation: immunosuppressants, corticosteroids, excess thyroid hormone, anticonvulsants (induce CYP450 and alter vitamin D metabolism)
Endocrine glands
Produce peptides, steroids and amines that control metabolism, growth, reproduction, and fluid and electrolyte balance
Adrenal medulla (NE, EPI)
Pancreas (insulin, glucagon)
Kidney (renin, 1,25 vitamin D)
Parathyroid glands (PTH)
Hypothalamic-pituitary-end organ axis
Corpus luteum/placenta
What body functions and behaviors does the hypothalamus regulate?
Body temperature, food intake, water balance, stress response, reproduction and social interaction, 5 senses
Which peptides does the hypothalamus release that act in the anterior pituitary?
Thyrotropin RH
Corticotropin RH
Gonadotropin RH
Growth hormone RH
Prolactin-inhibiting factor (dopamine)
Which peptides does the hypothalamus release (via neurons) that act in the posterior pituitary?
Oxytocin
Vasopressin (ADH)
Which peptides does the anterior pituitary release?
FSH
LH
ACTH
TSH
Prolactin
GH
(FLAT PeG)
What are the end-endocrine organ effects?
Adrenal cortex: glucocorticoids (gluconeogenesis, immunomodulation, vascular responsiveness to catecholamines), mineralocorticoids, adrenal androgens
Ovaries and testes: reproduction
Thyroid gland: skeletal growth, O2 consumption, nutrient utilization
What are some systemic and non-endocrine organ effects?
GH: protein synthesis, growth
Prolactin: milk production and secretion
DEXA (dual-energy x-ray absorptiometry) scan
Used to determine bone density
Scores reported relative to “young normals” or age-matched controls
Treatment for osteoporosis
Bisphosphonates
Teriparatide (PTH in short bursts)
Exercise
Ca2+ and Vitamin D3
Thiazide diuretics (has not been a clinical trial because thiazides are generic and no drug company to fund study, but thiazides help retain Ca2+, so when you give thiazide for HTN, just hope it has good side effect for osteoporosis!)
