Hall 11 - Heritable Effects of Radiation

Question 1

What is the annual average gonadal dose to a population adjusted for the relative child expectancy of that population?

Answer 1

Genetically significant dose (GSD)

Question 2

What form of sperm are the most radiosensitive?

Answer 2

Spermatogonia

Spermatozoa are the most resistant

*Latent period from RT exposure to decreased sperm count (10 week maturation process)

Question 3

What is the threshold dose for oligospermia?

Answer 3

0.15 Gy (after 6 week latent period)

Question 4

What is the threshold dose for transient azoospermia?

Answer 4

0.5 Gy

Question 5

What is the single dose for male sterility?

Answer 5

6 Gy

*Hormonal failure is induced at much higher doses

Question 6

What is the fractionated dose for male sterility?

Answer 6

2.5-3 Gy over 2-4 weeks

*Fractionated RT more damaging (unlike most normal tissues)

Question 7

What is the threshold dose for sterility in a prepubertal female?

Answer 7

12 Gy

Question 8

What is the threshold dose for sterility in a premenopausal female?

Answer 8

2 Gy

Question 9

How is female RT-induced sterility different from male?

Answer 9

No latent period
Hormone failure simultaneous
(no gonadal stem cells in females; all eggs present at birth)

Question 10

What is the doubling dose?

Answer 10

Dose that doubles spontaneous mutation rate

= 1-2 Sv

Absolute mutation rate is 0.1-0.6% per Sv

Question 11

How long should people wait to conceive after an acute RT exposure?

Answer 11

6 months
(heritable consequences are reduced with an interval)