Doctoral defence: Reeli Tamme “Associations between pubertal hormones and physical activity levels, and subsequent bone mineral characteristics: a longitudinal study of boys aged 12–18”

On 30 September at 14:00 Reeli Tamme will defend her doctoral thesis “Associations between pubertal hormones and physical activity levels, and subsequent bone mineral characteristics: a longitudinal study of boys aged 12–18”.

Supervisors:
Professor Vallo Tillmann, University of Tartu
Professor Jaak Jürimäe, University of Tartu

Opponent:
Professor Outi Mäkitie, University of Helsinki (Finland)

Summary
Osteoporosis is a significant public health problem. Peak bone mass obtained during first three decades plays an important role in the development of the disease. Since almost 95% of the peak bone mass is formed in childhood and adolescence, and the most critical period for the formation of bone tissue is puberty, the factors that affect accumulation of bone mass during puberty are important regarding future skeletal health.

There are several factors that affect bone formation. The most important biochemical factors are sex hormones, growth hormone together with insulin-like growth factor 1 and vitamin D, as well as several adipokines such as leptin and adiponectin. One of the most important factors affecting bone density is physical activity, which has effect on bone mass and bone mineral density through mechanical loading.

A cohort of healthy boys recruited at the Institute of Sport Sciences and Physiotherapy was followed annually at the age of 12, 13 and 14 years. As part of this dissertation the subjects were asked to come to the follow-up study at the age of 18 years. The main goal of the study was to investigate associations between serum testosterone, leptin to adiponectin ratio and physical activity in puberty and bone mineral characteristics at the age of 18 years. The final study cohort consisted of 88 healthy males who had most complete data set at all 4 study points.

We found that serum testosterone concentration at the age of 12 years is positively correlated with subsequent 6-year increase in total body bone mineral apparent density in healthy young males. Leptin to adiponectin ratio in puberty is negatively associated with lumbar spine bone mineral density and lumbar spine bone mineral apparent density at the age of 18 years as well as their increment between 12 and 18 years. Increased total physical activity and vigorous physical activity in puberty is associated with higher total body and femoral neck bone mineral density in healthy young males at the age of 18 years.