Thyroid hormones: The metabolic masters

Thyroid hormones are the metabolic masters of the body because they are the most important in regulating metabolism.

In my three previous articles, I discussed the importance of several hormones in regulating the functioning of the body and maintaining our health.

There are many more hormones that regulate the many different organ systems, but it is not necessary for you to know all of them. Many of these hormones were not even taught when I was in medical school about 40 years ago, and the ones that were taught have since been discovered to have many other functions than traditionally known.

The hormones which are the most important in regulating metabolism, and which also most often cause problems, are the thyroid hormones.

Thyroid hormones

Thyroid hormones are the main metabolic hormones, and influence the health of virtually all the organs in the body. The main hormones are thyroxine (T4) and tri-iodothyronine (T3), which is much stronger.

In fact, most T4 is converted to T3 in the body. Their levels are regulated by a feedback mechanism, which involves the thyroid stimulating hormone (TSH, or thyrotropin) from the pituitary gland, and thyrotropin releasing hormone (TRH) from the hypothalamus.

TSH is raised when T3 and/or T4 are low; and TSH is low when T3/T4 are high. TSH is therefore used to screen for the thyroid hormones. T3/T4 levels are then checked if TSH is abnormal.

However, there are certain conditions in which this feedback mechanism may be thrown out of sync.

For your complete hormonal profile, it is best to check all three.

The levels are often aberrant, that is why TSH is the only hormone routinely checked at birth, and is the only hormone routinely included in most "executive profile" blood tests that many of you may have done. It should also be routinely checked during pregnancy, as this story illustrates.

A thyroid story

About 25 years ago, when I was still delivering babies, a six-month pregnant patient was referred to me with problems of severe hypertension with gross swelling (oedema). She had what was termed "pre-eclampsia", or pregnancy-induced hypertension (PIH) with proteinuria (protein leakage in the urine).

Although the condition is relatively common, severe cases can rapidly deteriorate and the patient can have convulsions ("eclampsia"). This can have very serious consequences to both the mother and foetus.

That was precisely what happened to her. Even though I admitted her into the hospital, and administered all the necessary treatments, she started bleeding profusely from the gums, her BP skyrocketed, and she went into a coma. Her baby died, and her condition only improved after the baby was delivered.

Thereafter, she rapidly lost all the retained water, and her BP became normal. Since I had only seen her when she was bloated with water, she looked like a totally different person without the oedema. She was actually skinny and beautiful.

An inquiry into her past medical history revealed no significant medical problems. She had been seen by several other doctors before being referred to me. So I advised her to come for an antenatal check early for her next pregnancy, as the problem tends to happen earlier should it recur.

Sure enough, about two years later, she got pregnant again, and despite close monitoring and care, her BP shot up as early as the fourth month of pregnancy (usually it becomes a problem only during the last trimester, or after six months of pregnancy). She started bleeding from the gums and went into a coma again!

As before, the foetus died, and only after it was delivered (aborted) that she regained her health. Consultations with other specialists in the hospital did not help solve the problem.

So I told her that if she wanted to live, she should not get pregnant again, as she may not recover from a coma the third time (it would be worse if it were to recur, seeing that the problem started so early the second time).

Several years later, when she was 40 years old, she turned up at my clinic and announced that she was pregnant again. I was upset that she did not follow my advice, and at age 40, many other problems tend to occur.

She told me that she had gone to Mecca to pray in front of the Kaabah, and had asked God for a child. She had received an affirmative answer and was confident she would deliver safely this time.

I was flabbergasted. I was also dumbfounded, as her medical history indicated a horrendous prognosis. So I admitted her into the hospital from early pregnancy for intensive monitoring and treatment, with the plan that she would only leave hospital after her delivery (whatever the outcome).

In the meantime, I consulted my Sufi Shaykh about her. He supplicated to God, and then told me that God will take care of her, and God will guide me on how to manage her.

So it was, one day while I was doing my "ward rounds" at her bedside, I heard a whisper in my right ear. It said "check her thyroid hormones". I promptly did the test and the results showed that she had almost none!

That was surprising, because all her previous medical records did not show any thyroid problem, and when she was not pregnant, she did not have the symptoms or signs of hypothyroidism (low thyroid hormones).

At that time, thyroid screening was not routinely done in pregnancy, and nobody, not even my physician colleague who was consulted about her case previously, suspected that it could be hypothyroidism. We were all misled because PIH/pre-eclampsia is a well-recognised and common complication of pregnancy.

After correcting her thyroid problem, the pregnancy proceeded smoothly. However, even though everything that we checked for was normal, the foetus stopped growing at 32 weeks (ie eight weeks before her due date) and an emergency Caesarian delivery was done. I suspect that there were other hormones that needed to be checked that we were not aware of at that time.

Fortunately, the baby was healthy although she had to spend about one month in the incubator. It so happened that the operation had to be done on my birthday, so for the last 17 years, we celebrated our birthdays together. Incidentally, two of my own children also share the same birthdate as I!

This story illustrates that although hormone deficiency or excess is usually identifiable through classic symptoms or signs, it is not always so.

Furthermore, there are overlaps in the list of signs/symptoms of deficiencies/excess of the many different hormones, and it may be difficult to recognise and differentiate between them. The signs/symptoms may also be masked by other co-existing conditions.

In such cases, it can be easily missed, which is why a screening test for all is advisable.

Babies and children who are hypothyroid become physically and mentally stunted. Since all the organs are affected, prompt diagnosis and therapy are crucial.

Fewer children are hyperthyroid, which also requires prompt treatment.

Adults can become hypo or hyperthyroid (excess thyroid hormones). Hypothyroidism causes slowed metabolism, which leads to a slower heart rate, lethargy, intolerance to cold, sluggish reflexes, slow thinking, poor memory, poor immunity, low fertility, overweight, and many more signs and symptoms. In pregnancy, the worst-case scenario is described above.

Hyperthyroidism causes a different set of signs/symptoms that are related to the metabolism-boosting effect of the hormones - rapid heart rate, heat intolerance, increased sweating, nervousness, trembling fingers, weight loss, etc. Pregnant women with hyperthyroidism also face additional problems because pregnancy itself already means an extra burden on the heart and other organs.

Since thyroid hormones also decrease with age, the tendency for hypothyroidism rather than hyperthyroidism is greater. For most of us, it is about optimising the hormone levels which may be "normal" by laboratory standards, but do not give us the best possible metabolic function (see below).

Another thyroid story

Some years ago, someone recommended an American tourist to see me about her weight problem. She had tried dieting and exercise, but losing weight was so difficult. She had done her blood tests in the US and they were normal. She weighed 120kg.

After interviewing and examining her, I suspected she had slow metabolism, despite the "normal" blood tests. She only had one week to stay in Malaysia, so I decided to boost her metabolism to an optimal level, starting with a thyroid "extract" (which contains both T3 and T4).

Our doctors usually treat hypothyroidism using thyroxine (T4). T3 and thyroid extracts are not easily available here.

After a week of therapy, she came for follow-up and was extremely happy that she had lost 7kg without any extra effort. However, she told me that what she was most thankful for was not the weight loss, but that she had become energetic and "alive" again.

Since thyroid extracts are easily available in the US, I advised her to continue the treatment back home under her own doctor's care. Unfortunately, six months later, her husband was here in Kuala Lumpur and informed me that she was gaining weight again because her own doctor did not believe in the hormone optimisation therapy (because her results were "normal" to start with) and had refused to prescribe it to her.

This story illustrates that what is "normal" by laboratory guidelines, may not be what is optimal or best for you. For optimum health, we must realise that we are individuals with many similarities, but also many differences in how we function. What is good for one may not be enough for another.