Types of Osteoporosis

Type 1 or postmenopausal osteoporosis occurs in 5% to 20% of women, affecting those within 15 to 20 years of menopause with a peak incidence in the 60s and early 70s.
The incidence in women is eight times higher than that in men.
The frequency of postmenopausal osteoporosis accounts for the overall female-male ratio of 2:1 to 3:1.
Estrogen deficiency is thought to underlie this form of osteoporosis, rendering the skeleton more sensitive to parathyroid hormone (PTH), resulting in increased calcium resorption from bone.
This in turn decreases PTH secretion, 1,25-dihydroxyvitamin D production, and calcium absorption and ultimately causes loss of trabecular bone, leading to vertebral crush fractures and Colles’ fractures.
Women can lose around 2% to 3% of their bone per year for the first 5 years after menopause.
Because of the drop in estrogen production, women lose nearly 50% of their trabecular bone and 35% of their cortical bone throughout their lifetime, whereas men lose only 25% of both types of bone. At least 75% of the bone loss that occurs in women during the first two decades after menopause can be attributed to lack of estrogen rather than to aging. Bone loss associated with menopause does not begin with the onset of amenorrhea but may occur 1 to 3 years before the actual cessation of menstrual periods.

Type 2 or senile osteoporosis occurs in women or men more than 70 years of age and usually is associated with decreased bone formation along with decreased ability of the kidney to produce 1,25(OH)₂D₃.
The vitamin D deficiency results in decreased calcium absorption, which increases the PTH level and therefore bone resorption. In type 2 osteoporosis, cortical and trabecular bone is lost, primarily leading to increased risk of hip, long bone, and vertebral fractures.

Type 3 or secondary osteoporosis occurs equally in men and women and at any age. In men, most cases are due to disease or to drug therapy, but in 30% to 45% of affected individuals no cause can be identified. In various series of osteoporotic patients, secondary osteoporosis accounts for about 40% of the total number of osteoporotic fractures seen by a physician.
This type of osteoporosis is associated with a variety of conditions, including : hormonal imbalances (eg, Cushing’s syndrome); cancer (notably multiple myeloma); gastrointestinal disorders (especially inflammatory bowel disease causing malabsorption); drug use (eg, corticosteroids, cancer chemotherapy, anticonvulsants, heparin, barbiturates, valporic acid, gonadotropin-releasing hormone [GnRH], excessive use of aluminum-containing antacids); chronic renal failure; hyperthyroidism; hypogonadism in men; immobilization; osteogenesis imperfecta and related disorders; inflammatory arthritis (particularly rheumatoid arthritis); and poor nutrition (including malnutrition due to eating disorders).