Referring to the periodic table, Iodine is in the same group as Fluoride, Chlorine, Bromine and Astatine. The significance of this is that the outer electron rings of these elements have the same number of missing electrons (to complete the ring) and therefore have similar characteristics in their chemical behaviour. (This will be referenced again later in this article.)
Iodine is best known for its use in the thyroid system.
Goitre is a swelling of the thyroid gland at the front of the neck, most often brought on by a severe lack of iodine in the body. Whilst goitre is uncommon this does not indicate that iodine levels are sufficient for good health.
The thyroid gland under direction from the pituitary gland (the TSH hormone) produces the hormones T4 (Thyroxine), T3 (Triiodothyronine) and rT3(reverse T3).These hormones circulate around the body and ‘dictate’ the metabolic rate at which the cells should operate.
Simply put, this is the rate at which each cell does the work it has to do; in so doing it burns energy, produces chemicals, in particular proteins, divides and lots more.
The basal metabolic rate is the speed at which the cells are working when the person is at complete rest. If the basal rate is lower than what is considered normal the person has hypometabolism; if the basal rate is above the normal rate the person has hypermetabolism.
Obviously because of the energy consumption hypo ,with its lower energy requirement, tends to lead to overweight while hyper leads to under weight. Overweight and obesity is, however, a complex issue involving many co-factors and your metabolic rate should be checked if there is a problem. Your metabolic rate rises as you perform exercise, and some foods will also cause a rise.
Returning to the T4, T3, rT3.
T4 forms the bulk of the hormones produced by the thyroid. It is an inactive form and has four iodine atoms in each hormone. It circulates in the bloodstream readily available for conversion to T3, the active hormone. This conversion requires the removal of one iodine atom from the hormone. This is done by enzymes – de-iodinases, which require the elements Selenium and Zinc, the amino acid tyrosine and cortisol. Once converted the T3 can be used by cells to regulate the metabolic rate.
The thyroid also produces a quantity of T3, although not as much as T4.
The thyroid also produces rT3 – reverse T3.This is chemically identical to T3, the difference being the molecular structure. Why? – rT3 negates T3 in that it competes for receptor sites. The body can use this to slow down the metabolic rate when it chooses. For instance, slowing the rate may be useful if energy is in short supply (at the cellular level) or the body is under stress. Rather like hibernating.
Continued next week… | 
