This interactive module explores the biology of sex determination and development in humans, set against the backdrop of the different sex testing policies implemented throughout sports history.

The Click & Learn uses ongoing debates about the eligibility of certain female athletes to participate in women’s events as an entry point for students to learn the processes involved in human reproductive development. Students apply what they have learned to evaluate the results of different tests that have been used throughout sports history to qualify female athletes to compete.

After exploring the

Interactive Module

, please submit the completed Student Lab Sheet attached. By completing the Student Lab Sheet, you should be able to address the following:

• Describe how biological sex and gender differ from each other.
• Describe how mutations in a variety of genes can affect the development of internal and external sex characteristics.
• Explain how characteristics associated with biological sex may affect athletic performance.

This resource is provided by Howard Hughes Medical Institute.

Due Date Jan 31, 2020 11:59 PMAttachmentsSexVerification-StudentWS-CL (327.23 KB)Download All Files 

Developmental Biology Published January 2019

www.BioInteractive.org Page 1 of 2

Data Point
Student Handout

Testosterone Levels in Elite Athletes

Caption: Blood testosterone levels for 676 Olympic-level elite athletes. Individual athletes, represented by blue
dots, are grouped by their biological sex (“Men” or “Women”) and sport (1-Powerlifting, 2-Basketball, 3-Soccer,
4-Swimming, 5-Marathon, 6-Canoeing, 7-Rowing, 8-Cross-Country Skiing, 9-Alpine Skiing, 10-Weight Lifting, 11-
Judo, 12-Bandy, 13-Ice Hockey, 14-Handball, and 15-Track and Field). Blood samples were collected on a
voluntary basis within two hours after the athletes had competed in their events. Sports missing from the plots
did not have enough volunteers to be included in the study. None of the athletes were known to be intersex or to
have used performance-enhancing drugs.

Data Point
Student Handout

Testosterone Levels in Elite Athletes

Developmental Biology Published January 2019
www.BioInteractive.org Page 2 of 2

Testosterone is a hormone that is naturally produced by most
vertebrates. In humans, blood testosterone levels typically
range from about 0.5 to 2.5 nmol/L in women and 9 to 35
nmol/L in men. Scientists have investigated how testosterone
affects a number of characteristics in both sexes, including
sexual development and athletic performance. Because some
studies have shown that testosterone is associated with
increased muscle mass and strength in men, some people
have argued that athletes with higher testosterone levels
have certain advantages over their competitors.

In 2012, the International Association of Athletics
Federations (IAAF) and the International Olympic Committee
(IOC) created controversial rules that banned anyone with
testosterone levels above 10 nmol/L of blood from
participating in women’s sports events. These rules were
based on the argument that individuals with higher levels of
testosterone, which are more typical of those in men, would
have an unfair advantage in women’s events. In 2014, Indian
sprinter Dutee Chand was found to have natural testosterone
levels above the 10 nmol/L threshold. The IAAF banned her
from competing in national women’s track events. However,
a court case determined that the existing scientific evidence
did not justify the IAAF’s rules. As a result, the court
overturned the decision to ban Chand. Although the IAAF and
the IOC have since changed some of their rules, the debate
about regulating testosterone levels in competitive sports
continues.

In a 2018 study, scientists examined the testosterone levels
of Olympic-level elite athletes competing in national or
international sports events. The scientists measured
testosterone in blood samples from nearly 700 athletes to
determine whether the levels varied among athletes who
competed in different sports. The results were grouped
according to the athletes’ biological sexes and the sports they
competed in. From these data, the scientists made several
surprising observations about the athletes’ natural
testosterone levels. For example, several female athletes had
testosterone levels above 10 nmol/L, the threshold that the
IAAF had used to ban Dutee Chand from competing. In
addition, many male athletes had testosterone levels below
10 nmol/L.

OBSERVATIONS, NOTES & QUESTIONS
BIG IDEAS, NOTES & QUESTIONS
BACKGROUND INFORMATION

1. OBSERVATIONS, NOTES and QUESTIONS:
2. Big ideas, notes and questions: