Telogen Effluvium and Hair Length - Why are some hairs still short?

Why does a telogen effluvium (TE) produce hairs of all different lengths?

I am often asked why some patients with TE shed hairs of many different lengths - EVEN WHEN THE "TRIGGER" HAS RESOLVED.

I often explain this TE situation with an analogy. The story is fictional and meant to explain important points. (No disrespect should be interpreted to anyone who experiences such devastation in real life).

An Analogy

Imagine a factory that produces a wooden picnic tables. The factory normally produce 100 tables per day. But now the city where the factory is located has been hit by a storm which causes massive flooding and damage. 

Fortunately, the storm ends quickly and the city mayor officially declares the storm "over."  People are relieved and go about fixing things up.

The next day no picnic tables are made. People don't show up to work because they are busy fixing things at home and around the neighbourhood.

After a few days, a few people go back to work and 9 picnic tables get made - still under the normal production level of 100.

Normal production resumes

And then a massive shipment of trees comes in because of all the trees that have fallen down. The company foreman wants these trees used up quickly and offers 8 times the wage for anyone who comes into work. Now many people show up to work (even those who weren't scheduled). 120 picnic tables are made that day.

A Temporary Slow Down followed by an all time Record

But then a pipe bursts as the flooding had damaged an area in the factory that was not fully noticed. People are ready to work but only 12 picnic tables can be made the next day.

The pipe is fixed and people go back to work. 98 picnic tables are made that particular day and the next day an all time record of 135 tables is achieved.

 

Another Slow Down

But then fighting breaks out. There are just too many people for the factory. Not enough washrooms, no room in the lunchrooms. The refrigerator is overflowing with workers trying to store their lunch.

Picnic table production drops to 18.

Near normal production resumes again - for a short time.

The foreman builds more washrooms and buys more refrigerators. People are happy again and picnic table production climbs to 89.

And then there is a realization the illness has struck many in the city on account of the previous flooding conditions. Some fall ill. A limited number show up to work and production falls to 2 picnic tables per day.

Normal production

Eventually, the illness resolves. Everyone is healthy. The factory is ready to go. 100 picnic tables are produced everyday.

Conclusion

Now back to TE. For some patients with TE, the "factory" gets back up and running quickly with full efficiency. For these patients, shedding stops quickly and regrowth and shedding patterns are fairly normal after 3-5 months.

For other individuals with TE, there are a few glitches in the programming - even though the main "trigger" has long gone. These glitches can last a few months or even a few years.  Some hairs that are produces get shed too early because the hair cycle in that follicle is not fully functioning normally. We are not so lucky (yet) to know the reason for these glitches. (It is not so simple as a broken pipe or an overflowing refrigerator).

Most will find that the hair factory is fully operational by 12 months.