Is centrally induced alveolar bone loss in a large animal model preventable by peripheral hormone substitution?

Alveolar bone structures are mostly investigated in small animal models. The majority of these studies examined local influences on the alveolar bone, but only a few examined systemic influencing factors. The hypothalamic-pituitary axis is known to be essential for a vital bone balance. The aim of this study was to analyse the effects that selective hormone treatments have on alveolar bone structure and quality in a sheep model for alveolar bone loss, induced by hypothalamic-pituitary disconnection (HPD).

Thirty sheep were randomly selected into six groups of five each: control (C), ovariectomy-OVX (O), O + HPD (OH), OH with oestrogen treatment (OHE), OH with thyroxine (T4) treatment (OHT), and OH with a combined treatment of oestrogen and thyroxine (OHTE). After OVX and HPD procedures and an additional 9-month observation/treatment period, structural bone analyses of the mandible were performed by contact radiography, micro-CT, and static histomorphometry.

The HPD procedure caused structural alveolar bone parameters to decrease significantly compared to controls (C). Treatment with oestrogen (OHE) was protective and bone structure was maintained at baseline levels. Thyroxine treatment (OHT) promoted significant bone loss, but the combined treatment (OHTE) improved bone structure and volume parameters even above baseline levels.

Alveolar bone homeostasis significantly underlies systemic regulatory systems. Centrally induced (HPD) bone loss can be prevented by combined peripheral treatment with oestrogen and thyroxine.

These results demonstrate the significance of a balanced hormonal regulatory system for steady bone remodelling and maintenance of healthy alveolar bone.