Final answer:
The subject of the question is the gender eligibility of female swimmers in the Olympics.
Step-by-step explanation:
In the context of the question, it is stated that 'circumstances in which a particular athlete will not be eligible (by reason of hormonal characteristics) to participate in the 2012 Olympic Games' in the female category.' This suggests that the subject of the question is the gender eligibility of female swimmers in the Olympics.
In swimming, there have been instances where athletes with certain hormonal characteristics might not meet the eligibility criteria for the female category. For example, individuals with conditions like hyperandrogenism, which results in higher testosterone levels, might face restrictions on participating in the women's category.
Therefore, based on the given information, it can be concluded that the subject of this question is sports, specifically the gender eligibility of female swimmers in the Olympics.