Luís's Growth Was Influenced By Hormones

 Luís's Growth Was Influenced By Hormones

Epiphyseal growth

In our previous week's module we saw the importance of two hormones - PTH and estrogen - to bone health.  

Estrogen and another hormone, growth hormone, will be relevant to Luís's scenario.

Hopefully you saw in the animation

Links to an external site. and other information on the last page that our bones grow using a process similar to the way our skin grows.  In our epidermis we have a layer of keratinocyte stem cells that continuously divide and push the new cells away - in that case, toward the surface of the skin.  Near the epiphyses of our long bones, we again have rapidly dividing cells.  In this case they are rapidly dividing ("proliferating") chondrocytes.  As they push the new chondrocytes away from them, the cells form stacks that lengthen our bones.  That's how we get taller - lengthening stacks of dividing chondrocytes!  Then the osteoblasts replace the cartilage with bone and the process of bone formation is complete.
 

Growth hormone, which becomes more prevalent during puberty, stimulates division and activity in both chondrocytes and osteoblasts.  As a result, it tends to stimulate a more rapid growth in height.  As you learned last week, estrogen also stimulates osteoblast activity.  But estrogen also shortens the lifespan of chondrocytes!  Estrogen is released in increasing concentrations during puberty in both females and males.  Eventually, all those rapidly dividing chondrocytes in our epiphyses will die off due to the estrogen.  The osteoblasts then replace any remaining cartilage with bone and the epiphyseal cartilage is now gone.  What do you suppose that means for our potential to grow taller later in life?  Remember that this form of bone growth requires a cartilage model to be established first.