Final answer:
Disrupted hormonal regulation is a health consequence of being underweight, among other issues such as osteoporosis and a weakened immune system.
Step-by-step explanation:
The health consequence of being underweight that is correct from the options provided is disrupted hormonal regulation. Being underweight can contribute to a variety of health issues, including those related to bone health, such as osteoporosis, and hormonal imbalances that may affect menstrual cycles in women and sperm production in men. It can also lead to a compromised immune system, making an individual more susceptible to infections. Furthermore, undernutrition can increase the risk of infectious diseases, which can in turn further exacerbate undernutrition - a relationship depicted by both A and B options being correct in a separate context.