Polly: Fuad Lechin, MD, PhD, is an Emeritus Professor at the Central University of Venezuela. His team studies the effects that neurohormone imbalances have on diseases and the immune system. (See http://www.lechin.com/reasframe.htm.) Dr. Lechin´s team has found two types of neurochemical disorders in attention deficit hyperactivity. One presents excessive free serotonin in the plasma, while the other shows excessive dopaminergic activity plus norepinephrine overactivity.
If dopaminergic activity and norepinephrine activity are high, Dr. Fuad Lechin will sometimes balance the profile by administering serotonin precursors, like tryptophan or 5-HTP. However, in my opinion, this isn’t the first thing to try. If dopaminergic activity and norepinephrine activity are high, this could be due to the body’s inability to eliminate these and related amines. Low sulfates and/or a poor PST enzyme could be the reason these amines aren’t being eliminated. One could try supporting the PST enzyme with sulfates and the Feingold diet. 
Weak PST, high norepinephrine and/or high epinephrine is a possible manifestation of mercury poisoning.  So the child should be evaluated for mercury poisoning. Also check to make sure copper levels are adequate. Copper is important for the breakdown of many neurotransmitters.
What does one do if there is excessive free serotonin in the plasma? Dr. Lechin uses drugs favoring serotonin uptake at the synaptic level. However, as mentioned previously, there are other ways to reduce free serotonin. To stop the excessive free serotonin, a person needs to increase magnesium, eliminate food allergies, eliminate stress, eliminate much of the gramnegative bacteria in the intestines, and eliminate most of the polyunsaturated oils from the diet.
Polly: Ritalin and other drugs in the amphetamine family are often prescribed for people with attention deficit and sometimes for people with autism. Possible side effects are vomiting, confusion, delirium, headache, tachycardia, palpitations, cardiac arrhythmia, and high blood pressure. There are also reports of insomnia, growth impairment, weight loss stomach pains, appetite suppression, withdrawal, anger and restlessness.  If these drugs are tried, don’t go beyond the recommended dose. It is not safe to do so. There have been a few cases of suspected death (cardiac arrhythmia) from overdoses of Ritalin.
I would be particularly worried about starting a kid on thyroid supplements if they were still on Ritalin. Thyroid sensitizes the body to adrenaline (epinephrine). The presence of Ritalin might exacerbate some of the initial reactions to thyroid therapy, with potential serious consequences.
Amphetamines and methylphenidate (Ritalin) augment the effect of norepinephrine and dopamine in the brain. It is not the correct treatment for every child with attention deficit. From Dr. Fuad Lechin’s work, some of these children have high dopamine and norepinephrine activity, not low. Giving them Ritalin in this situation seems illogical. The kids should at least be tested for norepinephrine activity before placing them on Ritalin.
Polly: How do you test for norepinephrine activity? Ask your doctor for a test of total MHPG (3 methoxy-4-hydroxyphenylglycol).  If the total urinary excretion of MHPG is low, this suggests that smaller than normal amounts of norepinephrine are being released into the synapses of the brain.  (The total MHPG is usually low in autism, indicating reduced norepinephrine activity.)
An additional benefit of this test is that the ratio of MHPG sulfate to MHPG glucuronide will indicate if there is a sulfation or possible PST problem. If MHPG sulfate is low compared to MHPG glucuronide, then there may be a PST problem. If there is a PST weakness, then additional sulfates and the Feingold diet may be useful. Also, thyroid, particularly T3 thyroid, should improve sulfation.  This 24-hour urine test is available from SmithKline Beecham Clinical Laboratories.
There are rare occasions where a missing enzyme completely stops the production of norepinephrine in the body. This can be successfully treated with a drug called Ldihydroxyphenylserine. 
Polly: If you have tried everything else, and if testing shows that norepinephrine activity is low, then you may be tempted to fall back to Ritalin. However, you don’t have to use Ritalin to increase norepinephrine activity. Tyramine will release neuronal norepinephrine. Tyramine is an over-the-counter supplement. The body also creates it. Tyramine has been helpful in some cases of attention deficit.
Tyramine is created from tyrosine. (Tyrosine is an amino acid available in most health food stores. It is often mentioned as a treatment for attention deficit.) Theoretically, tyramine should work better than tyrosine for attention deficit because the body doesn’t have to do the conversion. Tyramine is abundant in many foods, however, there is a chance that the body is having trouble unbinding it. In this case, the free form found in tyramine supplements may be useful. As far as I’m aware, the unbound tyramine is presently only available from DEWS Twentyfirst Century Products, phone (940) 243-2178 or website http://www.DEWSnatural.com They call their tyramine product TAT.
DEWS also has a product called BHP. BHP has tyramine and threonine. The threonine helps improve the functioning of enzymes, including the desaturase enzymes (fat modifying enzymes). The threonine also helps defat the liver. If the liver works better, then all the neurohormones are more likely to be at correct levels, and eventually you may end up not needing the tyramine.
Folic acid, NADH, copper and vitamin C are important factors for the proper use of tyrosine. In particular, make sure there is adequate folic acid. Low folic acid is associated with low as well as excess dopamine. 
Before trying tyramine, you should make sure that the PST enzyme and sulfation are working well. Tyramine, norepinephrine and dopamine are removed via sulfation. You don’t want to put a strain on a weak sulfation pathway by giving the body more than it can handle.
More precautions: Be careful when using tyramine because tyramine, by increasing the production of adrenaline, may increase blood pressure. Tyramine should not be taken with the anti-depressant MAO inhibitor drugs. Also, if you are low on copper, your MAO can be low. So don’t take tyramine if you know that you are low on copper. You could end up with high blood pressure and hyperthyroidism. Too much tyramine all at once can initiate a migraine. So you may have to spread the dose out over the day.