Thyroid Physiology
Thyroid metabolism involves four important stages:
- Hormone Production. To produce thyroxine (T4) requires manganese, iodine, tyrosine, cyclic AMP, vitamin C, B-complex and other micronutrients.
Radiation toxicity, excessive oxidant stress or toxic chemicals can block hormone synthesis. Mercury and copper toxicity stimulate hormone synthesis.
- Hormone Release. Secretion of thyroid hormones requires sympathetic nervous stimulation. Many people have exhausted adrenals or other autonomic imbalances that may affect the sympathetic nervous system.
- Absorption into the Cells. Once released into the blood, T4 must be absorbed into the body cells. For this to occur, the cell membranes must function properly. Accumulation of biounavailable calcium and magnesium excessively stabilize cell membranes and reduce cell permeability. Deficient calcium and magnesium cause excessive cell permeability. Oxidant stress or impaired fatty acid metabolism or other damage to cell membranes can also block absorption of thyroxine.
Copper affects absorption by altering calcium and potassium levels. Cadmium or nickel toxicity affect hormone absorption by affecting the levels of calcium, sodium and other critical minerals.
- Utilization in the Mitochondria. Once inside the cells, thyroxine must be converted to to T3 and utilized in the mitochondria. Potassium plays a role in sensitizing the mitochondria to thyroid hormone. Fluorides in drinking water and chlorides found in bleaches used to make white flour are powerful inhibitors of thyroid hormone utilization. They interfere with iodine metabolism. Substances in soy and in raw cabbage, cauliflower and broccoli also inhibit thyroid hormone utilization. Foods that are most detrimental for one's thyroid are soy products and foods made with white flour. Many packaged foods processed with water contain high levels of fluorides that have found their way into water supplies.
Cells must also be able to respond to thyroid hormone stimulation. A range of vitamins and minerals are required for energy production in the glycolysis and carboxylic acid cycles in the mitochondria. If these co-factors are missing or toxins block steps in the pathway, thyroid hormone will be ineffective in increasing energy production.