I spent about 13 years as a vegetarian, over-exercising and slowly over time restricting more and more (soon after causing a binge eating disorder and bulimia) and exercising more and more. I developed bradycardia (36 bpm heart rate) and was on the path for a pacemaker. My blood pressure teetered around 89/58 and I could hardly stand up from a seated or squatting position without wanting to pass out.
I had lost my periods for 2 years and had become hypothyroid and was being pressured to take desiccated thyroid meds. Within 3 months of dedicated carnivore, my periods came back regularly, my resting heart rate settled at 50-55, my blood pressure came up to 95/67 and I no longer have any signs of low thyroid.