Symptoms

• Fracture after a minor fall or injury, such as a wrist, rib, hip, or vertebral fracture
• Sudden or persistent mid-back/low-back pain, sometimes from a vertebral compression fracture
• Loss of height or a stooped posture over time
• Repeated stress fractures, especially in athletes
• In some people, no pain or signs despite low bone density

Causes in young adults

• Low sex hormones: absent/irregular periods, early menopause, low testosterone, eating disorders, excessive exercise with inadequate nutrition
• Nutritional problems: low calcium/vitamin D intake, being underweight, malabsorption, coeliac disease
• Hormonal disorders: overactive thyroid, overactive parathyroid, Cushing syndrome
• Medicines: long-term steroid tablets such as prednisolone, some anti-seizure medicines, aromatase inhibitors, some cancer treatments, prolonged heparin
• Chronic illness: inflammatory bowel disease, rheumatoid/inflammatory disease, kidney or liver disease, diabetes, some blood disorders
• Smoking, heavy alcohol intake, prolonged immobility
• Rarely, idiopathic osteoporosis, where no cause is found

Diagnosis

• DXA bone-density scan
  • In premenopausal women and men under 50, the Z-score is generally more useful than the T-score.
  • A Z-score of -2.0 or lower means bone density is below the expected range for age, but it does not alone establish osteoporosis.
• Assessment for fragility fractures, including possible vertebral imaging
• Blood tests such as calcium, phosphate, alkaline phosphatase, vitamin D, kidney/liver function, thyroid-stimulating hormone, parathyroid hormone, full blood count, and hormone tests when appropriate
• Tests directed by the history, for example coeliac screening or evaluation for cortisol excess

Treatment

1. Treat the underlying cause
   • Correct vitamin D or calcium deficiency
   • Treat coeliac disease or other malabsorption
   • Review steroids and other bone-harming medicines with the prescriber
   • Treat thyroid, parathyroid, cortisol, or sex-hormone disorders
   • Address undernutrition, eating disorder, or menstrual loss
2. Lifestyle and fracture prevention
   • Adequate calcium from food, supplemented only if intake is inadequate
   • Vitamin D if deficient or at risk of deficiency
   • Regular weight-bearing and resistance exercise, tailored to fracture risk
   • Avoid smoking and limit alcohol
   • Maintain a healthy weight and adequate protein/energy intake
   • Avoid high-impact, twisting, or heavy spinal-loading activity if vertebral fractures are present until specialist advice is obtained
3. Medication
   • Medicines are not automatic for young people with low bone density.
   • They may be considered for recurrent fragility fractures, severe osteoporosis, ongoing high-risk steroid treatment, or when the cause cannot be corrected.
   • Options may include bisphosphonates, denosumab, or bone-building medicines such as teriparatide in selected high-risk cases, but selection needs specialist supervision.
   • For anyone who may become pregnant, this discussion is especially important. Some drugs can remain in bone for a long time, and evidence in younger adults is less certain than in postmenopausal osteoporosis.