Sunshine, Sleep, and the Science of Summer Growth Spurts

Dear Parents,

Have you ever watched your child stand next to their classmates and wonder, “When are they going to catch up?” Maybe the other kids are getting taller, voices are changing, and your child just… isn’t.

Believe it or not, summer might be the season when those differences feel most obvious. But there’s a biological reason for that.

Several studies — including one published in the American Journal of Physical Anthropology — have found that children tend to grow more rapidly in the spring and summer months. The common denominator? Hormones.

Longer daylight hours naturally increase vitamin D levels, a nutrient essential for calcium absorption and healthy bone development. Vitamin D also plays a regulatory role in hormone production, including growth hormone and steroids like estrogen and testosterone, both of which are critical for normal development during childhood and adolescence.

The increase in outdoor activity during the summer months comes into play as well. Our parental instinct to have the kids "get outside and play" is spot on! That activity of course leads to physical stimulation and higher energy expenditure, both of which can impact metabolism and growth signals.

And lastly, summer usually means fewer early wake-ups. When kids get more sleep — especially deep, uninterrupted sleep — their bodies have more opportunity to release growth hormone. In fact, The Journal of Pediatrics determined that the majority of growth hormone secretion (70-80%) occurs during slow-wave sleep!

So if your child seems to be lagging behind their peers in height or other signs of puberty, this season offers an ideal window to check in. A summer physical can give us insight into how their endocrine system is functioning, and whether there’s anything we can do to support them!

Warmly,
Dr. Penny