Recognizing when people are symptomatic, or on thyroid medication while on a medically, supervised weight loss program is key to successful weight loss. Thyroid function can reduce by as much as 50% 30 days into any diet. Recognizing this fact is key to a successful diet experience. If this sounds like something you experience, this is where Diet Doc stands out with their prescription hCG diet that addresses thyroid function. Symptoms include: weight loss can stop or slow down, cold hands and feet, losing more hair when you brush or after showering than normal.