<< Return to Blog

Understanding Thyroid Lab Tests

By Kenneth N. Woliner, M.D.
Posted: Thursday, June 10th, 2010

Mary was frustrated. She always had trouble keeping a normal weight, but after having her second child two years ago, she couldn’t shake the extra forty pounds she gained. Mary became so fatigued that any amount of exercise seemed impossible. Previously, she would do Spinning classes three times a week, but now, she had not made it to the gym in six months. “I haven’t given up,” she protested. “They still take their dues out of my checking account every month.” Mary’s skin got so dry and oily that her face broke out in acne. Her moods took a turn south, and that led to binge eating in front of the TV. When her primary care doctor wanted to put her on anti-depressants, Mary found her way to my office.

After taking a detailed history and performing a complete physical exam I said, “I think your thyroid condition is under-treated.”

“How could that be? My other doctors said my thyroid tests were normal!”

“Unfortunately, they only did one type of test. Despite being called ‘ultra-sensitive’, the ‘TSH’ blood test has its limitations.1 It isn’t accurate for everyone.”

“Shouldn’t an endocrinologist know which blood tests to order?”

“My mentor, Dr. Richard Shames, author of the book ‘Thyroid Power’, talks about how patients are tyrannized by this one test, and how the doctors who rely upon it often withhold effective medication.2 Perhaps it was their training that emphasized blood tests over listening to patients, or it could be that they make so much money doing lab testing, that they have come to rely upon labs almost exclusively. Regardless, this one test, despite saying you are ‘normal’, doesn’t prove that you don’t have a real medical condition that requires further treatment. I would like to do a more complete workup.”

Mary returned a week later to review her lab results. “After draining me of all my blood, I hope you know what to do to make me feel better.”

“I’m sorry – being a family practitioner, I look at other things besides thyroid. Being overweight can be caused by lots of things, thyroid being only one of them. But I will say this, your tests definitely say you are under-medicated.”

“Now you’re going to tell me to increase my Synthroid by 0.025 or something like that.”

“Actually, no. The word ‘doctor’ means ‘to teach’. I want to spend the next half-hour teaching you what these tests really mean. By the end this visit, I think you will know more about thyroid disease than most endocrinologists. Later on, when you learn more, I want you to help choose among options of what to do next. In my opinion, the days of paternalism in medicine are long over. I want you to take an active role in your care.

“Let’s start with that first test, the TSH. It stands for ‘Thyroid Stimulating Hormone’ – the substance your brain makes to tell the thyroid to make more thyroid hormone. To help you understand how this works – I want to make a metaphor to a cold apartment in Minnesota . If it is really cold, the thermostat (your brain) will send lots of electricity (TSH) to the boiler (your thyroid gland) to make lots of heat (thyroid hormone). As the apartment heats up, the thermostat will still send some electricity, but maybe not as much, to still make heat, but only enough to keep the apartment at the right temperature. If there is a raging fire in the apartment (or a space heater right next to the thermostat), the thermostat won’t send any electricity to the boiler and no heat will be produced.”

“So where’s my TSH at? I’m sooooooo cold right now. Can I borrow your lab coat?”

I handed my coat to Mary. “Here you go. Your TSH is at 0.02 with normal being from 0.5 to 5.5.”

“Wait! By this test – I should be taking less medication, not more. I already feel cold. Please don’t decrease my dose. It’s hard enough getting out of bed already.”

“Don’t worry – I’m not decreasing your dose. I said you were under-medicated and I meant it. This test doesn’t say you’re getting too much medication. On the contrary, it proves that you are NOT getting too much.”

“But I’m outside the normal range. The other doctors always decreased my dose when that happened. And I always felt worse when they did. Promise you won’t take away my medication?”

“I understand your fear, but stop for a second and remember the metaphor. When there is too much heat in the apartment, such as the danger of a fire, NO electricity goes to the boiler. I do not think you have a raging fire inside you. The mere fact that your TSH is detectable signifies that you don’t have too much thyroid hormone in your body. I know you’re not overmedicated because you are still making TSH. Your body is asking for more heat.”

“But why am I outside the normal range?”

“Every test has the potential for error, and we call them type 1 and type 2 errors. Type 1 error is when we think that there is something there when it really isn’t. It happens when a test is very sensitive (it picks up most disease), but is not specific (it tests positive when no disease is present). Type 2 error is when the test is very specific (it doesn’t label you with a disease if you don’t have one), but not sensitive enough (it misses you, even if you do have a medical condition).3 To prevent too many ‘false positives’, too many people from being called ‘Hypothyroid’ when they are indeed normal, the lab makes a cutoff at some point. Unfortunately, their cutoff point cuts off many patients from getting proper treatment. We call them ‘false negatives’.”

“I would think in a disease like HIV, you really would want to make sure someone had it before you labeled them, but low thyroid doesn’t have that stigma. I don’t understand why they do things this way.”

“Perhaps another time we’ll talk about the science or politics of medicine, but for right now I want to assure you, you are not getting too much medication.”

“Okay, let’s move on. But you said I definitely was under-medicated. How do you know?”

“There are actually three sets of tests that are even more important than the TSH. Let’s go through them. The first set describes the levels of free hormones in your blood stream. I test for ‘Free T4’ and ‘Free T3’. ‘T4’ describes a thyroid molecule with four iodine atoms attached to it. ‘T3’ is the same thing, but with one of them lopped off. It actually is four times as potent as T4, so I test for both. I no longer test for Total T4, Total T3, Free Thyroxine Index (FTI), and T3 Resin Uptake (T3RU). They can be thrown off by toxic chemicals and drugs (lead poisoning, birth control pills, hormone replacement therapy, seizure medication, blood pressure and cholesterol drugs (Propranolol, Gemfibrozil), and high dose aspirin (used for arthritis)); deficiencies of vitamins and minerals (Vitamin E, Selenium, others…), and chronic disease (liver and kidney disease, Parkinson’s Dementia).4 he only reason to continue to draw those tests is to bill you or your insurance company. They don’t change prognosis or medical management one iota.”

“You seem a little jaded.”

“I’m sorry – I sometimes get a little carried away. I just get upset when doctors do tests that do little to help their patients, just to line their pockets. And even if a ‘nameless, faceless’ insurance company is paying for that testing, it comes back to the patient eventually. The insurance company raises the premiums the employers pay. The employers pass on these premium increases to their employees, or worse yet, drop coverage altogether. I have quite a few patients in that situation. It just isn’t right.”

“No. It isn’t.”

“Back on subject – the Free T4 and Free T3. For this lab, the normal for Free T4 is 0.8 to 1.8. You’re only at 1.2. For Free T3 – normal is 230 to 420. You are even lower here – coming in at 240. To make sense of this, in the marathon of life – you might still be in the race – but instead of finishing first, second, or third – you’re an also-ran.”

“It seems my other doctors want to wait until I’m out of the race with a broken ankle before doing anything to help me. What other tests do you got there?”

“Other tests are used to determine hyperthyroidism and thyroid hormone resistance. I actually didn’t waste your money drawing a Thyroglobulin. It is elevated for a variety of reasons, and really is only useful to follow patients after have been treated for differentiated thyroid cancer.5 It isn’t useful for predicting thyroid cancer. There are other modalities used for that. If you would like – come to the local hospital where my next lecture will be: ‘Thyroid Cancer – Holistic approaches to diagnosis and treatment.’6 I didn’t do a test for ‘TSH Receptor Antibodies’ or the ‘TSH following TRH (Thyroid Releasing Hormone) as you do not have symptoms or signs of hyperthyroidism. I also didn’t do a ‘Reverse T3’. Some people, especially when they are deficient of vitamins and minerals, or exposed to toxic amounts of cadmium or mercury, have trouble converting T4 to T3. Instead, they make ‘Reverse T3’, a form that doesn’t work. Unfortunately, most doctors are totally unaware of the Reverse T3 phenomenon, and even worse, most labs do not properly assay for it.7 Your HMO insurance doesn’t pay for labs to be sent to any of the few reference labs around the country that actually perform a reliable assay, so I didn’t bother drawing the test. With the common laboratories around here, it always comes out normal, even when there is a real problem.

“The next two tests you’ll find very interesting. They are called ‘Thyroid Antibodies’, and come in two forms, ‘Anti-Microsomal (Thyroid Peroxidase) Antibodies’ and ‘Anti-Thryoglobulin Antibodies’. These often elevate postpartum.8 I notice your symptoms got worse after having your second child.”

“Yes, I haven’t been able to do anything at all. What were my numbers?”

“They were off the chart. Normally, they should be undetectable, but yours were 1,532 and 939 respectively. You have Hashimoto’s Thyroiditis. You may have even had these antibodies all your life. here is no way to know. The other doctors never tested you for them.”

“I’m mad, that’s true. But right now I just want to get better. What do I need to do now? And when will I need to come back to be retested?”

“Interestingly enough, you will never need another thyroid blood test again.”

“Back up a minute… Didn’t you say I had Hashimoto’s Thyroiditis? Don’t you need to follow my blood counts every three months like the other doctors have been doing?”

“These blood tests – they don’t work for you. They didn’t help you over the last 15 years you’ve been having problems, even when your problems became worse over the last two. It is because these thyroid antibodies variably bind up the hormones you have. There is no way to tell how much thyroid hormone you need based upon blood tests.”

Mary’s eyes were rolling back into her head and her mouth was sagging open. She obviously needed more of an explanation. “Let’s try another analogy. When a traffic helicopter flies overhead, it sees all the cars on the road – and says, ‘There’s plenty of transportation to take people around the city.’ But what if a meter maid noticed they didn’t pay their parking tickets and put a red parking boot on some of them. They wouldn’t be able to go anywhere. In order to have enough transportation for the city – you might need twice as many cars. Unfortunately – there is no way to know how vicious that meter maid is – we just know that she is there. There is no way to know how much of a negative effect those thyroid antibodies are having, we just know that they are there. The presence of thyroid antibodies throws off every thyroid test, including the TSH.”

Mary was exasperated. Slumping back in her chair, “Then how will I ever know how much medicine to be on?”

“You forgot, there is one more type of testing that will be most effective for you.” Mary became interested again and leaned forward. “We should test the effect that thyroid hormones have on your body. With hormone resistance, it is often easier and more effective to test the function of the hormone, not the actual level. This idea isn’t new. In Type II Diabetes, we know there is insulin hormone resistance. We don’t check insulin levels – we check what it does by monitoring your blood sugar levels. There are many different types of thyroid hormone resistance. In addition to the Reverse T3 phenomenon and Thyroid Antibodies, some people are deficient of essential fatty acids or other vitamins, limiting thyroid hormone’s ability to get into the brain or other cells to have its full effect.9,10 We just have to check what thyroid hormone does in your body.

“Though active thyroid hormone is needed to lower cholesterol and blood pressure, to raise blood sugar when hypoglycemic, and to convert beta-carotene into Vitamin A, there is no specific blood test to show whether thyroid hormone is working properly or not. Dr. Broda Barnes, MD, PhD, who wrote one of the first books on hypothyroidism, ‘Hypothyroidism: the unsuspected illness’, described a simple temperature test using a mercury thermometer.11 Mercury thermometers are more accurate than digital ones, and because they are hard to find nowadays, I’ll sell one to you for a dollar (that’s all they cost me). Here is a handout to describe how to do the test.

“Lastly, I want you to take this sheet of paper that has ten, 10-point scales on it. I want you to write down the ten things most important to you. For the first line, fill in ‘Energy Level’. Zero will be where you can’t get out of bed, ten being where you are excited about travel and are planning a fun trip. If you are spending money you don’t have, you might be at a twelve. Please call me before they take away your credit cards.” Mary smiled. “Fill in the other nine items with the things most important to you: weight, skin, and mood are three things you’ve already mentioned. Many people also put down constipation, hair growth/loss, nail quality, and cold/heat intolerance, menstrual periods, and libido. Lastly, there are checkboxes at the bottom for ‘Palpitations’ (sensations of your heartbeat) and ‘Anxiety’. If you feel like you have too much coffee or caffeine in your system, you might be getting too much medication. Every so often, scale yourself. If you are getting better – then we know you are on the right track.”

“I think I finally understand these tests, so what do we do now? You said I would have options in choosing my own care.”

“You do. Because you are lower in T3 than T4, and because many of my patients report they feel better when they add some T3 to their regimen, I think whatever you choose should include that.12 Some people will take two pills, perhaps the Synthroid (a pill that contains synthetic T4 only) you are on now, plus another pill called Cytomel (a pill that contains only synthetic T3). Other people that were never really happy on T4 alone find it easier to switch completely to a combination product that has both T4 and T3 in it (Armour Thyroid, Nature Thyroid, others…). Armour Thyroid, which has been around for over 100 years, is standardized by the USP (and is more stable than Synthroid), and has the advantage of costing only $0.12 / pill wholesale. Many people that do not have insurance prefer it for price reasons alone. What do you think you want to do?”

“I didn’t much like that Synthroid, and since my health insurance doesn’t pay for medications, that Armour Thyroid sounds like a good idea. But what dose to we start at? How often do I need to come to see you?”

“The equivalent dose to what you are on is only 30 mg (or if using old apothecary units – one half grain). Let’s start with that, but I’ll give you lots of pills. After two weeks, if your scales are not close enough to ten, and you haven’t had any side effects such as palpitations or anxiety, increase by one pill a day. You can do this each two weeks up to four pills a day (120 mg) without causing any long term side effects. Please go slowly. Dosing thyroid is almost like running on ice. It takes a while to get the full effect of the medicine, but if you increase too quickly – you hit the wall (palpitations).”

“But what about osteoporosis? Every time I begged my endocrinologist to give me more medication, he said my bones would become thin and break. I don’t want that to happen. I’m short enough as it is!”

“I said we wouldn’t have to do any more blood tests for thyroid, but you will have to be monitored. Fortunately, doses less than 120 mg (2 grains) per day of Armour Thyroid (equivalent doses would be 200 mcg/day Synthroid/Levoxyl (T4) or 50 mcg/day Cytomel (T3)) have been studied long term and do not cause any long-term side effects, not even osteoporosis. In fact, those taking thyroid had thicker bones than those patients not on medication! 13 Doses greater than that have not been studied, so to be safe, we will need to do annual bone density screening if we go higher than 120 mg/day. Lastly, Hashimoto’s Thyroiditis can cause osteoporosis in of itself. We should do a baseline test now.

“I plan on seeing you in two months – that will give you enough time to see if you need 120 mg or less. I hope that you will eventually learn how to manage your condition on your own and we can space out these visits. When you are in control, you probably won’t have to see me for thyroid but once a year.”

Mary’s bone density was well within normal limits. Her energy, weight, skin and mood all normalized on a dose of 90 mg of Armour Thyroid per day, costing her only $7.11 / month from the local pharmacy.14 As she didn’t need any more thyroid blood tests, nor excessive visits each month with a doctor – she saved some money to buy Christmas gifts for my office, as well as for her husband and two children.

REFERENCES: 1Lueprasitsakul W, et al. Flavonoid administration immediately displaces thyroxine (T4) from serum transthyretin, increases serum free T4 and decreases serum thyrotropin in the rat. Endocrinology 1990; 126:2890. 2Shames RL and Shames KH. Thyroid Power: ten steps to total health. Harper Resource; ISBN: 0060082224; 2002. 3Kirch W. Misdiagnosis at a university hospital in four medical areas. Medicine ( Baltimore ) 1996;75(1): 29-40. 4Becker DV, et al. Optimal use of blood tests for assessment of thyroid function. JAMA. 1993; 269:2736-7. 5Franklyn JA, et al. Free triiodothyronine and free thyroxine in sera of pregnant women and subjects with congenitally increased or decreased thyroxine binding globulin. Clin Chem 1983; 29(8):1527-30. 6Woliner, KN. Thyroid Cancer – Holistic approaches to diagnosis and treatment. 7Wilson JD, et al. Editor. Williams textbook of endocrinology, 9th ed. W.B Saunders Company 1998. ISBN 0-7216-6152-1. pps 297-404. 8Stagnaro-Green A. Recognizing, understanding, and treating postpartum thyroiditis. Endocrinol Metab Clin North Am 2000: 29(2):417-30. 9Maenpaa J, Liewendah K. Peripheral insensitivity to to thyroid hormones in a euthyroid girl with goiter. Arch Dis Child. 1980; 55:207. 10Brent Ga. The molecular basis of thyroid hormone action. N Engl J Med 1994; 331:847-853. 11Barnes BO and Galton L. Hypothyroidism: the unsuspected illness. Ty Crowell Co; ISBN: 069001029X; 1976. 12Toft AD. Thyroid hormone replacement – one hormone or two? N Engl J Med 1999; 340:469-470. 13Franklyn JA. Long-term thyroxine treatment and bone mineral density. Lancet 1992; 340(8810):9-13. 14Price Quote: Walgreen’s Pharmacy – Boca Raton ; October 26, 2002 .

Comments are closed.