Low thyroid tends to cause low energy levels, cold intolerance and weight gain.
Excess thyroid causes higher energy levels, feeling too warm and weight loss.
The crucial nutrient for thyroid hormone synthesis is iodine. Iodine is also available in ocean fish and can be supplemented by taking kelp concentrate. Estrogen, progesterone and thyroid hormones are interrelated. Estrogen for example, causes food calories to be stored as fat while thyroid hormones causes fat calories to be turned into usable energy. Thyroid hormone and estrogen therefore have opposing actions.