Common Questions
What are the mechanisms of bone loss in anorexia nervosa?
Mechanisms of bone loss in anorexia nervosa include:
- Estrogen deficiency: Anorexia nervosa is one cause of hypothalamic hypogonadism, resulting in decreased estrogen levels. Studies comparing anorexic women to women with other causes of hypothalamic amenorrhea have shown that women with anorexia have more severe osteopenia than those with hypothalamic amenorrhea, suggesting that estrogen deficiency is not the only cause of bone loss in these women (1).
- Malnutrition: Fasting, even over a period of several days, has been shown to result in decreased bone formation. In addition, bone density correlates with indices such as caloric intake, body mass index, and fat intake (2).
- IGF-1 deficiency: There is evidence to suggest that IGF-1 deficiency contributes to the bone loss found in anorexic patients. IGF-1 stimulates DNA and collagen synthesis and decreases collagen degradation. Anorexic women are severely IGF-1 deficient, and the deficiency increases with weight loss, improves with weight gain, and is correlated with bone loss. (3) One study has found that short-term administration of IGF-1 increases markers of bone formation in anorexic women (4).
- Elevated cortisol levels and decreased calcium intake: While hypercortisolism and decreased calcium intake are present in patients with osteoporosis and are both risk factors for osteoporosis, studies have not shown them to be correlated with bone density in patients with anorexia nervosa (4).
Given that they are known risk factors, however, they may play a small role in the bone loss experienced by these patients (5).
- Grinspoon, et al. Severity of osteopenia in estrogen-deficient women with anorexia nervosa and hypothalamic amenorrhea. Journal of Clinical Endocrinology and Metabolism 1999; 84: 2049-2055.
- Grinspoon SK, Baum HB, Kim V, Coggins C, Klibanski A. Decreased bone formation and increased mineral dissolution during acute fasting in young women. J Clin Endocrinol Metab 1995; 80(12): 3628-33.
- Counts DR, et al. The effect of anorexia nervosa and refeeding on growth hormone binding protein, the insulin-like growth factors (IGFs), and the IGF-binding proteins. Journal of Clinical Endocrinology and Metabolism 0000; 75: 762-767.
- Grinspoon S, Baum H, Lee K, Anderson E, Herzog D, Klibanski A. Effects of short-term recombinant human insulin-like growth factor I administration on bone turnover in osteopenic women with anorexia nervosa. Journal of Clinical Endocrinology and Metabolism 1996; 81(11): 3864-3870.
- Grinspoon SK, Herzog DB, Klibanski A. Mechanisms and treatment options for bone loss in anorexia nervosa. Psychopharmacology Bulletin 1997; 33(3): 399-404.