Role of Thyroid Hormones in Autism & Asperger's:

Living on a university campus for many years, it is common knowledge that the thyroid, a
gland hanging in the front of the neck could present a problem to many women and few men.
Young adult women with protruding eyeballs and bitchy attitudes are known to have
hyperthyroid or overactivity of the thyroid gland. More mature women gaining weight
inexplicably and feeling cold are said to have hypothyroid or underactivity of the thyroid gland.
No one ever mentioned or even alluded to the place of children in this equation. Like a trusting
young man, I went about my business believing that thyroid problems are specific to adults,
mostly women. One day as a third year medical student, I passed through a pediatric rotation.
Out of curiosity, I found out that all healthy newborns are subjected to a battery of tests in the
first 24 hours of their life. The tests performed vary from state to state. However the thyroid
test is a fixture in all states. To my shock, I asked the resident in charge about the purpose of
including a thyroid test for infants. She said, children with thyroid problems lag behind on
mental development and may grow up with IQ (intelligent quotient) in the lowest 10th

Needless to say I was astonished at the selectivity of information flow from the medical
authorities. But then I was on a mission to find out more about this hidden “secret” of
medicine. What I found out is likely to shock you too. The thyroid hormone is primarily a
developmental hormone. Like growth hormone, its most crucial importance is early in life. Like
growth hormone it is much less important in adulthood. In fact, there is ample evidence that in
adults, supplementing with thyroid hormones can accelerate the cell life-cycle.

Each cell in the body has a certain limit on how long it can function. After the cell exhausts its
resources it undergoes a natural death. The length of time it takes for a cell to reach the end of
its life is dependent on the burden it has to carry. A heavier burden is more likely to exhaust the
cellular resources sooner and lead to an earlier cell death. Thyroid hormones in adults,
especially triiodothyronine, will force the average cell is forced to function at a higher level
while reducing its efficiency, wasting so much energy as heat eventually leading to an earlier
cell death. Therefore, the effect of thyroid hormones on adults heightens short-term
performance of tissues at the expense of the long-term longevity of tissues – and people. In real
life terms, supplementing with thyroid hormones is the equivalent of liquidating one’s retirement
assets and using them to buy a yacht at age 40. In fact the multiple levels of synergy between
thyroid hormones and adrenalin point to that same theme of overutilizing future reserves today.
But then who am I to judge!

Having challenged the whole paradigm of thyroid problems as the mainstream looks at them, let
us go back and examine the importance of thyroid hormones in a growing infant through
puberty. In general, that same property of thyroid hormones increasing the metabolic rate –
energy production and utilization – takes on a different goal in children. A growing infant needs
to increase the metabolic rate to much higher levels than in adults. This is important for the
timely accomplishment of the numerous stages of development leading up to the mature adult
shape and mental acuity. During childhood while cells and tissues are attempting to reach a
mature level of functionality and a stable environment, the effect of thyroid hormones will
enhance that goal of maturation.

Let us examine some of the major functions of thyroid hormone during infancy and childhood.
Triiodothyronine, the most active thyroid hormone:

1- Stimulates growth hormone production and release; in fact the thyroid hormone is a
necessary requirement without which growth hormone cannot be adequately produced.

2- Stimulates bone growth and strengthening and eventual bone maturation later after puberty

3- Stimulates neuronal growth and development; specifically, stimulates dendritic growth. The
dendrites are similar to antennas the neurons [main brain and nerve cells] use to communicate
with the surrounding environment and other neurons. Children learn through utilizing,
strengthening and growing more of these connections between neurons.

4- Stimulates myelin production in the brain, a magical substance necessary for speeding up
signal transmission in the brain; Without myelin, the signal will slow down dramatically that it
may take the child considerably long time (minutes or longer) for example to move her neck in
the direction of a voice or to respond when called. Myelin is not only important to speed up the
signal. It is also important to prevent signal extinction. Without myelin the electric signal
flowing through a neuron may quickly lose momentum before it reaches its target. The myelin
acts as relay and reinforcement stations aimed at re-energizing a fading signal. Signal extinction
essentially means that the intent to move or speak determined by the brain does not get
implemented since the muscles did not get the message.  

5-The thyroid function in myelin production and distribution goes further. Thyroid hormone
helps in determining the proper order of myelination of neurons in various parts of the brain.
For example, the midbrain structures involved in fulfilling basic needs such as crying and
yelling for food will need to be myelinated and developed years earlier than a higher function – e.
g. frontal cerebral cortical – involved in appreciation of abstract paintings.

6-Stimulates development of the cerebellum, a brain structure that plays a critical role in motor
skills (lifting of the head, sitting upright, crawling, walking and so forth).

7- Stimulates development of the retina, an inner eye structure necessary for discriminating
distances and colors and faces and appreciation of three-dimensional objects and so forth.

8- Thyroid hormone does not increase the metabolic rate in the brain. It does not
indiscriminately increase the activity of enzymes the same way it does in the rest of the body.
Thyroid hormone however has very selective role in stimulating certain enzymes involved in
regulation of multiple essential neurotransmitters including GABA, aspartate, acetylcholine and
others. These chemicals are collectively essential for proper growth, social and intellectual

The thyroid hormone in human infants is involved in both growth and differentiation of multiple
body parts. For example, it promotes bone elongation and helps in strengthening the bone partly
through adding calcium and phosphates (ossification). However, thyroid hormone is crucial in
determining the final length of every given bone. In this way, the thyroid hormone is helping in
equipping the bone for its ultimate role in supporting healthy movement but it is also defining
the limits of this function at the same time through helping determine the final length and
thickness of this particular bone. This is very important in the sense that any excess or
deficiency of thyroid hormone during childhood development may lead to irreversible variation
in the competency of several body parts.

Developmental effects of hypothyroidism:

A deficiency in thyroid hormone in childhood leads to inadequate physical growth, short
stature, and significant impairment in mental and cognitive development. Plainly stated, thyroid
hormone is needed for learning, intelligence, eyesight development and bone frame growth to
name a few central functions.


Non-responsiveness or delay in response when called by name
Clumsiness and difficulty grabbing objects, sitting up, crawling etc… at the expected time frame
Difficulty forming intelligible phrases and sentences after the expected time frame for this
Difficulty discriminating objects based on color or depth
Changes in appetite or emerging aversion to certain foods

Developmental effects of hyperthyroidism

Overabundance of thyroid hormone on the other hand accelerates the differentiation function
making it outpace growth. For example the final structure and role of a bone is determined
under elevated thyroid hormone conditions before the bone has had a chance to grow in length.
A similar example can be said of the growth of essential neurons and surrounding myelin in the
brain. Overabundance of thyroid hormone may lead to advanced differentiation and assignment
of many brain structures before they have had the chance to develop the speed and connections
needed for full functionality.

At least in animal studies it has been shown that the impact of thyroid hormones on brain
development operates within a narrow optimal window. Low concentrations of thyroid
hormone as we have just seen may have detrimental impact on brain development. At the same
time, excessive concentrations of thyroid hormone may impair spatial learning capacity. This
refers to orientation to three-dimensional objects and situations. In addition, excessive thyroid
hormone (hyperthyroid) may prevent the long-term development of facilitated learning
pathways. For example when a child is exposed to her car seat several times, she usually
develops an ability to operate the mechanics of the seat that becomes natural for her. This
means that the brain has developed a facilitated path that learned to handle the car seat, so she
does not have to learn every time to handle the seat from anew. This facilitated path not only
helps a child know how to handle the car seat but also makes it easy to learn how to handle
similar objects in other contexts. Excessive concentrations of thyroid hormones can potentially
impair this ability for long-term retention of working memory and generalization of learning.

What can I do as a parent?
1-encourage your doctor to consider testing your child for thyroid problems:
Today, every newborn is tested for thyroid function at birth in most states. This is a good start.
The traditional thinking of the absolute necessity of abundant thyroid hormone during the first
three months of life is certainly true. However, after having secured the ample presence of
thyroid hormone during this critical developmental window, the thyroid influence on growth
and differentiation does NOT end. Thyroid problems may not appear at birth and may develop
or become apparent at any point during childhood until puberty and beyond. Furthermore,
functional and transient thyroid problems can happen anytime during human development.
Newborns showing normal thyroid function at birth can still encounter thyroid problems later in
childhood. Thyroid function testing should be considered an integral part of the assessment of
children showing signs of delayed physical or mental development. It should also be considered
for periodic screening in sensitive children even without specific symptoms directly related to
thyroid problems. There is usually a time delay between an objective and significant change in
thyroid hormone concentration and the appearance of observable symptoms.

2-look into appropriate dietary and life-style changes listed in the table below:


SOY: All soy containing foods (including soy milk) facilitate the disposition of thyroid hormone
from the body

CRUCIFEROUS VEGETABLES (Broccoli, Cauliflower, Brussels, kholrabi…): All crucifers
contain a chemical (isothiocyanate) which is a toxin for the thyroid gland

GLUTEN CONTAINING GRAINS (RYE, BARLEY, WHEAT…): Gluten sensitive individuals
of all ages show a deterioration in thyroid function while consuming grains; and an
improvement on gluten-free diet

(hydrocortisone), a naturally occurring steroid, in excess amounts may lower active thyroid
hormone in the body

cortisol show a more accentuated effect compared to cortisol

LEMON BALM (Melissa Officinalis): an herb commonly used to help with sleep may reduce
thyroid function

Melatonin supplements: Melatonin and other sleep aids also may lower levels of active thyroid

Low carbohydrate diets: May lower levels of active thyroid hormone in body

Hypothyroidism in children: diagnosis and treatment.
Setian NS. J Pediatr (Rio J). 2007 Nov;83(5 Suppl):S209-16

The role of thyroid hormone in fetal neurodevelopment
Morreale de Escobar G. J Pediatr Endocrinol Metab. 2001;14 Suppl 6:1453-62.

Hypothyroidism and pregnancy: impact on mother and child health
Menif O, Omar S, Feki M, Kaabachi N. Ann Biol Clin (Paris). 2008 Jan-Feb;66(1):43-51.

Thyroid hormones states and brain development interactions.
Ahmed OM, El-Gareib AW, El-Bakry AM, Abd El-Tawab SM, Ahmed RG. Int J Dev Neurosci.
2008 Apr;26(2):147-209

Reflections on mental retardation and congenital hypothyroidism: effects of
trace mineral deficiencies
Sidibé el H. Sante. 2007 Jan-Mar;17(1):41-50

Thyroid hormones, learning and memory.
Rivas M, Naranjo JR. Genes Brain Behav. 2007 Jun;6 Suppl 1:40-4.

Neonatal hyperthyroidism disrupts hippocampal LTP and spatial learning
C. Pavlides, B. S. McEwen et al. Experimental brain research 1991; vol 85(3): 559-564

The Role of Thyroid Hormone on Testicular Development and Function
Wagner M, Magaginin S, Maia AL. J Endocrinol. 2008 Aug 26

Author: Rami Serhan, MD
Medical consultant
Sovereign Research
(206) 659-1ASD (273)

Note: this article is an excerpt of the upcoming book, “PSYCHE-SMART AUTISM”.
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