Question:

I usually wake up during the night, mostly one or two hours after I fall asleep. It usually takes me a while to fall back to sleep again. I am 17 so I`m greatly concerned about my height which directly relates to the release of human growth hormone (HGH) during deep sleep. I learned that the largest burst of HGH is released within the first two hours of sleeping cycle. Therefore, I would like to know if HGH is still released normally after I get awakened in the first two hours of sleep and then fall back to sleep again? I also tried to extend my sleep to make up for it, did that really help?

Answer:

Growth hormone (GH) is released in a stable low level throughout the day with bursts of secretion that occur mainly at night. As you correctly mentioned, the largest burst of GH occurs shortly after sleep onset and is tightly associated with the onset of deep or slow wave sleep (SWS). This pattern is most pronounced in men, in whom the largest, and often the only burst during a 24-hour period, occurs in the first 2 hours after sleep onset. In women, daytime GH bursts occur more commonly and the burst associated with sleep onset is less pronounced.

As mentioned, the relationship between GH and sleep is primarily related to the onset of SWS, which occurs within the first few hours of sleep. Several studies have confirmed this relationship and documented that the maximal amount of GH release occurs within minutes of the onset of SWS. It is estimated that 70% of the total GH release during sleep occurs during SWS. There is a clear association between the amounts of GH secreted during sleep and the duration of the slow wave sleep cycles during the sleep episode. This occurs even if your sleep cycle is changed to a different time period (as in shift workers, who will still have GH release associated with SWS even though they may sleep during the daytime). However, it should be noted that GH release also occurs before the onset of sleep and thus SWS is not the only time it is secreted.

Awakenings and sleep disruption tend to decrease the release of GH. In studies of GH secretion, investigators found that whenever sleep was disrupted, the secretion of GH was abruptly suppressed with every awakening. Overall, it is well accepted that sleep fragmentation can decrease GH secretion.

In your case, it is notable that you are probably getting the largest amount of SWS in the first couple of hours of sleep, before you awaken for the first time. And even though you may awaken then, when you fall back to sleep, you will continue to cycle through SWS during the night. Furthermore, if you are sleep deprived or having severely fragmented sleep, SWS is the first stage of sleep to rebound during recovery sleep. In short, as long as you are getting an adequate amount of sleep for your age (probably 8-9 hours) and your sleep is not being interrupted by another process (such as a sleep disorder, environmental noise, etc), it is likely that your are getting adequate amounts of SWS and GH secretion.

The role of GH in determining height at the age of 17 is not clear, as it is more important in influencing height in earlier years, when SWS is a much large percentage of the overall sleep time. It is noteworthy that several factors aside from GH levels play a role in determining the height of a particular individual.

From a sleep standpoint, I suggest that you make sure you are practicing good sleep hygiene (see website) and ensure you are obtaining adequate sleep on a regular basis – these are the best things you can do for your growth and development. And finally, if you are concerned that the sleep disruption is affecting your daytime functioning or causing other problems for you, then it may be worthwhile discussing this with your general practitioner. A referral to a Sleep Specialist may be indicated if the problem is significant enough.

For more information:

Go to the Sleep Disorders health topic.