Hormonal, chemical and thermal inhibition of spermatogenesis: contribution of French teams to international data with the aim of developing male contraception in France.

Plain-language summary

This is a history of forty years of French research into male contraception (hormonal, chemical and thermal) summarising clinical trials involving thousands of men and couples. Those trials established that deliberately raising the temperature of the testicles suppresses sperm production reliably enough to be tested as a contraceptive, which is about as strong a demonstration as exists that scrotal heat drives sperm counts down. On contraception itself the verdict was mixed: all three approaches did inhibit sperm production, but side effects, chiefly loss of libido, awkward modes of administration, and a high proportion of men who did not respond, kept any of them from coming into general use. The authors note the work paid off elsewhere too, in understanding how toxic compounds damage sperm production and how fertility might be preserved.

Key findings

• Deliberately raising testicular temperature suppressed sperm production reliably enough to be trialled as a contraceptive method.
• Hormonal and chemical methods also inhibited sperm production effectively.
• Side effects, mainly loss of libido, plus awkward administration and a high rate of non-responders, prevented any method reaching general use.
• The same research improved understanding of how toxic compounds affect sperm production.