The pineal and thymus glands are endocrine glands that play important roles in regulating circadian rhythms and the immune system. The pineal gland produces melatonin which regulates sleep cycles and inhibits sexual development before puberty. The thymus gland produces T cells which help the immune system fight infections, and its production of hormones is important for immune system maturation. Diseases can arise if these glands are dysfunctional, disrupted, or damaged, leading to issues like sleep disorders, early puberty, immunodeficiency, or autoimmune disease.

1. The Pineal & Thymus
Glands

2. Pineal Gland: Physical
Characteristics
•Small, pine-cone-shaped gland (hence its name)
•Reddish-gray in color
•It is larger in children, but shrinks with the onset of puberty
•In adults, it weighs a bit more than 0.1 grams and is about 0.8
cm long
•Situated between 2 cerebral hemispheres ; Attached to the
posterior wall of the 3rd
cerebral ventricle
•Suspended in a cavity of cerebrospinal fluid
•Lacks a blood-brain barrier, therefore, receives blood, oxygen,
& nutrients through a rich vascular network
•Contains a large supply of adrenergic nerve fibers
•Composed of pinealocytes (endocrine cells with extensions
that interact with the extensions of nearby cells) and supporting
cells that resemble astrocytes

4. Pineal Gland:
Chemical
Characteristics
Structural Formula of melatonin
•It contains a number of neuropeptides & neurotransmitters such
as somatostatin, norepinephrine, serotonin, and histamine.
•Somatostatin is a hormone that inhibits the secretion of several
hormones, including growth hormone, insulin, and gastrin.
•Norepinephrine is the main neurotransmitter that regulates its
melatonin secreting activity.
•Serotonin is a neurotransmitter that helps maintain a "happy
feeling," and seems to help keep our moods under control by
helping with sleep, calming anxiety, and relieving depression.
•Histamine is neurotransmitter that causes inflammation and
several allergic symptoms.
•However, melatonin, a derivative of tryptophan, is the only
hormone secreted by the gland.
•The chemical formula of melatonin is C13H16N2O2.

5. Pineal Gland:
Molecular
Characteristics
•It is developed from epithelial tissue
•The soft tissue of the adult pineal
gland contains more fluoride than any
other soft tissue in the body - a level of
fluoride capable of inhibiting enzymes.
•The pineal gland also contains hard
tissue(hyroxyapatite crystals), which
accumulates more fluoride than any
other hard tissue in the body (ex. teeth
and bone)
•Studies show that fluoride reduces the
levels of melatonin in the blood

6. Functions of the Pineal Gland
 The major function of the pineal gland is producing melatonin, a
hormone that has several important effects on the body.
 Melatonin regulates daily body rhythms, most importantly circadian
rhythm, the wake/sleep cycle. We feel sleepy at night because
darkness stimulates the pineal gland to produce melatonin and we
feel alert during the day because light inhibits the pineal gland from
producing melatonin. Since the activity of the pineal gland depends
on the amount of available energy, it is a photosensitive organ.
 The abundant levels of melatonin in children inhibit the secretion of
gonadotropins, hormones that regulate normal growth, sexual
development, and reproductive functions, before puberty. Therefore,
they prevent the onset of puberty before the appropriate age.

7. Functions of the Pineal Gland cont’d
 Melatonin levels are low in children with autism, and as a result, about 70% of them suffer from
sleeping problems.
 Studies show that low doses of melatonin can help children with autism sleep better without
giving them any noticeable side effects.
 Studies show that melatonin levels may be related to the risk of certain types of cancer.
 Melatonin levels tend to be lower in women with breast cancer than in those without the disease.
 Laboratory experiments show that low levels of melatonin stimulate the growth of certain types of
breast cancer cells. However, adding melatonin to these cells slows their growth.
 New research also suggests that melatonin may strengthen the effects of some chemotherapy
drugs used to treat breast cancer.
 In one study, several women with breast cancer were given melatonin 7 days before beginning
chemotherapy. The melatonin prevented the lowering of platelets in the blood, a common
complication that can cause bleeding.

8. Functions of the Pineal Gland cont’d
 In another study, several women with breast cancer were taking tamoxifen, but were not improving.
However, once melatonin was added, the tumors in over 28% of the women modestly shrank.
 Studies also show that melatonin levels are lower in men with prostate cancer than in those without the
disease.
 In test tube studies, melatonin blocks the growth of prostate cancer cells.
 In one small-scale study, melatonin, along with improved regular medical treatment, improved survival
rates in 9 out of 14 men with metastatic prostate cancer.
 Melatonin has been found to be able to slow the aging process.
 It is a powerful antioxidant that can easily pass through cell membranes and the blood-brain barrier.
 It is a highly effective and direct scavenger of the very reactive and toxic free radicals.
 Unlike other antioxidants, melatonin does not undergo redox cycling. Once it is oxidized it can never be
reduced to its former state. Therefore, it never promotes free radical formation.
 By terminally disarming the free radicals, melatonin protects the cells’ DNA from oxidation damage.

9. Pineal Gland: Interactions with Other
Organs

Secretion of melatonin by the pineal gland inhibits the secretion of the
Gonadotropin-releasing hormone (GnRH) by the hypothalamus.

Secretion of melatonin also indirectly inhibits the pituitary from secreting
gonadotropins, Leutenizing Hormone (LH) and Follicle Stimulating Hormone
(FSH), because the secretion of GnRH is necessary for this to occur.

Because its secretion reduces the levels of LH in the blood, melatonin may
inhibit ovulation in women and can decrease sperm mobility and sex drive in
men.

The pineal gland also interacts with the hypothalamus in regulating the
circadian rhythm.

10. Pineal Gland: Diseases & Disorders

One sleep disorder is Delayed Circadian Rhythm Disorder. DCR constitutes a mismatch
between you external and internal clocks. Your internal clock runs slower than a normal
circadian rhythm which is a 24-hour period so your body doesn't 'wake up' until later in the
morning or day.

When this occurs in the body, the pineal gland releases the nighttime hormone,
melatonin, too late, often causing you to fall asleep later. When its time to wake up, your
body clock believes it’s only midnight and is still producing the nighttime hormones.

As a result of this disorder a person may experience the following symptoms:

Difficulty falling and staying asleep, and or late night insomnia.

A general lack of energy in the morning.

An increase of energy/mood in the evening or late at night.

Difficulty concentrating, being alert, or accomplishing tasks

Some DCR sufferers oversleep and have trouble getting up

Treatment:

Dawn Simulation helps people maintain a steady circadian rhythm by exposing their
internal body clocks to a properly timed signal of light through their retina. The
light gradually becomes brighter, simulating a sunrise, to reset the body clock while not
to bright to cause premature awakening.

11. Diseases & Disorders cont’d

Advanced Circadian Rhythm Disorder (ACR) is the opposite of DCR. With ACR, your
internal body clock is running faster than a normal circadian rhythm. You tend to run out of
energy before their day is up. ACR compresses the sleep portion of your daily cycle, causing you to
lose valuable sleep. ACR sufferers often sleep less than 8 hours per night, and awaken early.

Because your circadian rhythm is running fast, your pineal gland releases melatonin too
soon, causing lethargy earlier in the day. Then, because melatonin is released prematurely, you are
unable to maintain a complete sleep cycle, and you wake up too early.

As a result of this disorder a person may experience the following symptoms:

Early morning awakening and/or early morning Insomnia

Inconsistent sleep with one or more awake periods during the night

Lack of energy during the day, feeling tired in the early afternoon and/or evening

Alertness and ability to function may also be diminished

Some ACR sufferers may not notice a sleep problem but lose energy and feel tired or down in
the afternoon or evening time.

Treatment:

Specialized bright light is the only effective treatment for ACR. Bright light will inhibit the
release of melatonin for about 3 hours. Use bright light in the late afternoon and
evening and avoid bright morning light before 9:00 am. Where sunglasses if you need
to be exposed to bright light early in the morning and make your night time as dark as
possible.

13. Diseases & Disorders cont’d

Precocious Puberty: An unusually early onset of puberty beginning before age 8 for girls and before age 9 for
boys.

If left untreated, children will become able to reproduce and will stop growing too soon.

One of the causes for precocious puberty is having lower than normal levels of melatonin. This is a problem
because melatonin is responsible for inhibiting the actions of the gonadotropins.

Symptoms for girls are breast growth and a first menstruation

Symptoms for boys enlarged testicles and penis, facial hair, and a deepening of the voice

Symptoms for boys AND girls are pubic or underarm hair, rapid growth, acne, and adult body odor

If the children’s precocious puberty is caused by abnormally low melatonin levels, melatonin supplements can be a
very successful form of treatment.

Treatment is very important because precocious puberty will prevent children from reaching their full height
because they stop growing too early.

Going through puberty before anyone their age can also have negative psychological effects on children, including
low self-esteem and depression.

15. Thymus Gland: Physical Characteristics
•Pinkish-gray color in children and yellow in adults
•Soft
•About 5 cm long at birth
•Continuously grows during childhood
•Begins to steadily atrophy after puberty until it is
ultimately replaced by adipose tissue
•Largest and most active in children
•Weighs between 20 and 37 grams, its maximum
weight, by puberty
•Made up of two identical lateral lobes
•Each lobe is composed of lobules that are held
together by delicate areolar tissue, and the thymus
as a whole is enclosed in a protective capsule
•The two lobes are slightly different in size and can
be joined together or separated
•Located in the thoracic cavity, just below the neck
and behind the sternum
•Divided into two parts, the outer cortex and inner
medulla.

16. Thymus Gland:
Molecular
Characteristics
 Made up of mucosa-associated
lymphoid tissue
 Lymphoid tissue mostly consists of
lymphocytes, but it is also rich in
macrophages and reticular cells
 The thymus is enclosed by a thin
connective tissue capsule
 Each lobule consists of medullary tissue
with numerous lateral extensions, each
of which is covered by a layer of cortical
tissue
 Between lobules are connective tissue
septa, extensions of the capsule
containing arterioles and veins.
 With age, there is a heavy accumulation
of fat associated with the connective
tissue

17. Functions of the Thymus Gland
 The thymus produces and processes a white
blood cell called a T-lymphocyte. These T
cells help cells recognize and destroy
invading bacteria, viruses, abnormal cell
growth, and foreign tissue.
 The T cells travel from the bone marrow to
the thymus gland where they remain until
they are activated. After they mature, the T
cells enter the blood stream and travel to
other lymphatic organs to act as a defense
mechanism against diseases.
 The thymus gland produces thymosin, a
hormone that stimulates T cells in other
lymphatic organs to mature. It also
produces thymopoietin, another hormone
which is protein present in the mRNA and is
encoded by the TMPO gene.
 The thymus gland has a reputation for
becoming underactive which may lead
to the development of
immunodeficiency diseases.
 Thymosin also plays a role in the
initiation of the aging process.

18. Thymus Gland: Interactions with Other
Organs
This gland is responsible for development of the
lymphatic system, which plays a major role in the
immune and waste removal systems.
If the thymus’s development is hindered in any way in
the fetus, the whole of the immune system cannot
develop.
The thymus also contributes to the immune system by
producing and processing T Lymphocytes (see functions
for T Cells’ duty)

19. Thymus Gland: Diseases & Disorders Thymus Cancer
 Thymus cancer develops when malignant cancer cells
form on the outer surface of the thymus gland. There
are primarily two kinds of cancer that can arise in the
thymus.
 The first type involves a thymoma, a tumor whose
cancerous cells look like normal thymus tissue.
 Thymomas are linked to autoimmune diseases
which cause the immune system to attack healthy
tissue.
 The second sort of thymus cancer includes thymic
carcinomas, tumors which contain cells that do not
look like thymus cells.
 Thymic carcinomas are exceptionally dangerous
because they grow more quickly and will more
probably extend to other tissues.
 Both thymomas and thymic carcinomas can be present
in an individual without triggering any symptoms and
may only be found in a routine chest x-ray. But when
symptoms do occur, it is most commonly in the form
of a continuing cough, chest pain, and trouble
breathing.

20. Diseases & Disorders cont’d
 DiGeorge Syndrome (Thymic Dysplasia)
 DiGeorge syndrome is a rare congenital defect that causes dysfunction of a
number of different tissues.
 Patients with DiGeorge syndrome have a small deletion on their 22nd
chromosome, known as 22q11.2, which contains between 20 and 30 genes
responsible for the development of different parts of the body.
 Often, in DiGeorge syndrome, a symptom is having a very small or absent
thymus gland.
 As a result of having DiGeorge syndrome, patients will have very weak immune
systems and are extremely prone to infections.
 Patients may need to receive a thymus transplant or receive infusions of immune
cells to help prevent dangerous infections.

21. Diseases & Disorders cont’d
 Myasthenia gravis is a chronic autoimmune neuromuscular disease characterized by varying
degrees of weakness of the skeletal muscles
 Myasthenia gravis is caused by a transmission malfunction of nerve impulses to the muscles.
 In myasthenia gravis, antibodies produced by the body’s own immune system obstruct, change, or
destroy the receptors for acetylcholine at the neuromuscular junction, which inhibits the muscle
from contracting.
 In adults with myasthenia gravis, the thymus gland remains large and is abnormal. It contains
certain clusters of immune cells indicative of lymphoid hyperplasia—a condition usually found only
in the spleen and lymph nodes during an active immune response. Some may develop thymomas
which are generally benign, but can become malignant.
 The relationship between the thymus gland and myasthenia gravis is not yet fully understood.
Scientists believe the thymus gland may give incorrect instructions to developing immune cells,
ultimately resulting in autoimmunity and the production of the acetylcholine receptor antibodies,
thereby setting the stage for the attack on neuromuscular transmission.
 Thymectomy, the surgical removal of the thymus gland, reduces symptoms in some individuals
without thymoma and may cure some people, possibly by re-balancing the immune system.
 Most common in women under 40 and men over 60.