Is there such a thing as seasonal telogen effluvium?

This needs an in-person evaluation. I suggest seeing a hair loss expert now to evaluate and go over your condition and provide you information about your best treatment options. There are great non-invasive options like prp/progesterone and/or hair transplantation. See an expert. Best, Dr. Emer

Several research studies have shown that humans living in northern regions tend to shed more during the late summer and early autumn months.   Most of the time this goes undetected, but some individuals do notice this feature. A second phase of increase shedding in human beings may occur in Spring as well. While changes could be due to vitamin D the reality is that they probably aren’t. REFERENCES1) Courtois M et al. Periodicity in the growth and shedding of hair. Br J Dermatol 1996; 134;47-54.
2) Kunz M et al. Seasonality of hair shedding in healthy women complaining of hair loss. Dermatology 2009; 219: 105-10.
3) Randall CA and Ebling EJG. Seasonal changes in human hair growth.  Br J Dermatol 1991; 124: 146-51.

excessively low vit. D may cause hair loss. Stress, anemia, lupus, medications, hormonal and seasonal changes, nutritional problems, severe diets, bulimia, protein/calorie deficiency, zinc and essential amino-acid deficiency, mal-absorption (intestinal and digestive problems), A-vitamin excess, general anesthesia, affective mood disorders are also causes of hair loss.