Radboud University
Endocrinology
Syllabus
Gül Turan
June 2020
The literature and figures in this syllabus are gathered from virtual lectures and PowerPoint
slides provided by the lecturers.
,Index
Introduction to endocrinology .............................................................................................................. 3
1. Histology of the endocrine glands ............................................................................................ 5
1.1 The epithelium ....................................................................................................................................... 5
1.2 Hypophysis/pituitary ............................................................................................................................. 5
1.3 Adrenal gland ........................................................................................................................................ 6
1.4 Thyroid gland ......................................................................................................................................... 7
1.5 Pancreas ................................................................................................................................................ 7
1.6 Ovaries ................................................................................................................................................... 7
1.7 Testes ..................................................................................................................................................... 8
2. Mechanisms of hormone action .............................................................................................. 10
3. The hypothalamus-pituitary axis ........................................................................................... 12
4. The endocrinology of the adrenal gland ................................................................................ 13
5. Steroids of the adrenal cortex – RAAS .................................................................................. 16
6. Catecholamines of the adrenal medulla................................................................................. 18
7. The thyroid gland and thyroid hormones ............................................................................. 20
8. Endocrinology of the pancreas ............................................................................................... 22
9. Female reproduction ............................................................................................................... 24
10. Male reproduction ................................................................................................................... 26
11. Hormones and tumours .......................................................................................................... 28
12. Leptin and energy homeostasis .............................................................................................. 29
13. Endocrinology of the digestive tract ...................................................................................... 31
33
14. Growth hormone ..................................................................................................................... 34
35
15. Calcitropic hormones and osteoporosis ................................................................................. 36
16. Pre-virtual lab class questions: A hormone and its receptor............................................... 38
17. BRC report virtual lab class: A hormone and its receptor.................................................. 40
2
,Introduction to endocrinology
Endocrinology is the study of the endocrine system in the human body. This system regulates the
functioning of every cell, tissue, and organ in the body. It is about communication between cells using
signalling molecules (hormones) carried by the blood. These hormones are most often secreted by
glands. However, besides endocrine communication there are other types of communication pathways
between cells. With paracrine communication, signals diffuse locally and act on neighbouring cells.
Whilst autocrine signals act on the same cell that secretes them. There are also neurocrine and
neuroendocrine pathways. In the neurocrine pathway, communication goes through neurotransmitters.
Within neuroendocrine, signals released from neurons end up in the blood.
Hormones work in different ways. This mainly depends on
the chemical structure of the hormone. There are four main
classes of hormones (signalling molecules):
1. Peptides and proteins – These are the largest group
and are sequences of amino acids. An example is
insulin or TSH releasing hormone (TRH)
2. Eicosanoids – Are derivatives from fatty acids and
are predominantly involved in paracrine signalling.
An example is prostaglandin.
3. Steroids – Have a four ring backbone structure and
are derived from cholesterol. These are mainly
produced in the adrenal cortex and gonads. Some
examples are cortisol, testosterone and oestradiol.
4. Amines – Are derived from tyrosine. Examples are
dopamine, adrenaline, thyroxine.
Figure 1 Pathway and pathologies in steroid
biosynthesis.
The hormone levels in the body are regulated through a feedback mechanism loop. Most often this is
a negative feedback mechanism. When a hormone is needed, the production of that hormone will be
stimulated. However, if you reach a point where you have enough of that particular hormone present,
production of that hormone will be inhibited. Another way to regulate hormonal levels could be by a
positive feedback mechanism. In this case, the feedback would increase the production of the hormone
rather than inhibit the production.
The earliest study on endocrinology began with Arnold Berthold in 1984. He discovered that castrated
cockerels did not develop combs and did not exhibit male behaviour. When he replaced the testes back
of the same bird it resulted in normal behaviour and development. Hereafter, he concluded that the testes
secreted a substance that was responsible for the development of the secondary sex characteristics.
Hereby, he concluded that the nervous system did not play a role in this effect.
Another scientist who had a role in understanding endocrinology was Ivan Pavlov. Pavlov investigated
the gastric function of dogs. He removed the oesophagus of dogs and therefore created a fistula. By
adding HCl into the duodenum he observed the reaction of the pancreas, which secreted bicarbonate as
a result. Pavlov believed that the aforementioned result was due to the nervous system. However,
William Bayliss and Ernest Starling proved that Pavlov was wrong in 1902. They performed an
experiment similar to Pavlov’s in which they removed all nervous connections and instilled acid into
the duodenum. This caused the pancreas to secrete. They observed the same response after injecting an
extract of the jejunum mucosa into the jugular vein. In this case some factor in the mucosa was
responsible. They named this factor/substance “secretin” and the first hormone was therefore
discovered.
3
, There are different ways to visualize and detect hormones. These methods predominantly use the
specificity of antibodies. Immunohistochemistry, immunofluorescence and western blot are three
examples in which antibody specificity is used. Within immunohistochemistry a primary antibody
detects the target antigen. A secondary antibody binds to the primary antibody. Usually the secondary
antibody is conjugated with a detection molecule which can further catalyse a colour producing reaction.
Immunofluorescence is based on the same technique as immunohistochemistry. The only difference
within immunofluorescence is in the detection signal, which is a fluorescent signal. Another technique
is the western blot method. This technique is based on immunochromatography where proteins are
separated into a polyacrylamide gel according to their molecular weight.
4
Endocrinology
Syllabus
Gül Turan
June 2020
The literature and figures in this syllabus are gathered from virtual lectures and PowerPoint
slides provided by the lecturers.
,Index
Introduction to endocrinology .............................................................................................................. 3
1. Histology of the endocrine glands ............................................................................................ 5
1.1 The epithelium ....................................................................................................................................... 5
1.2 Hypophysis/pituitary ............................................................................................................................. 5
1.3 Adrenal gland ........................................................................................................................................ 6
1.4 Thyroid gland ......................................................................................................................................... 7
1.5 Pancreas ................................................................................................................................................ 7
1.6 Ovaries ................................................................................................................................................... 7
1.7 Testes ..................................................................................................................................................... 8
2. Mechanisms of hormone action .............................................................................................. 10
3. The hypothalamus-pituitary axis ........................................................................................... 12
4. The endocrinology of the adrenal gland ................................................................................ 13
5. Steroids of the adrenal cortex – RAAS .................................................................................. 16
6. Catecholamines of the adrenal medulla................................................................................. 18
7. The thyroid gland and thyroid hormones ............................................................................. 20
8. Endocrinology of the pancreas ............................................................................................... 22
9. Female reproduction ............................................................................................................... 24
10. Male reproduction ................................................................................................................... 26
11. Hormones and tumours .......................................................................................................... 28
12. Leptin and energy homeostasis .............................................................................................. 29
13. Endocrinology of the digestive tract ...................................................................................... 31
33
14. Growth hormone ..................................................................................................................... 34
35
15. Calcitropic hormones and osteoporosis ................................................................................. 36
16. Pre-virtual lab class questions: A hormone and its receptor............................................... 38
17. BRC report virtual lab class: A hormone and its receptor.................................................. 40
2
,Introduction to endocrinology
Endocrinology is the study of the endocrine system in the human body. This system regulates the
functioning of every cell, tissue, and organ in the body. It is about communication between cells using
signalling molecules (hormones) carried by the blood. These hormones are most often secreted by
glands. However, besides endocrine communication there are other types of communication pathways
between cells. With paracrine communication, signals diffuse locally and act on neighbouring cells.
Whilst autocrine signals act on the same cell that secretes them. There are also neurocrine and
neuroendocrine pathways. In the neurocrine pathway, communication goes through neurotransmitters.
Within neuroendocrine, signals released from neurons end up in the blood.
Hormones work in different ways. This mainly depends on
the chemical structure of the hormone. There are four main
classes of hormones (signalling molecules):
1. Peptides and proteins – These are the largest group
and are sequences of amino acids. An example is
insulin or TSH releasing hormone (TRH)
2. Eicosanoids – Are derivatives from fatty acids and
are predominantly involved in paracrine signalling.
An example is prostaglandin.
3. Steroids – Have a four ring backbone structure and
are derived from cholesterol. These are mainly
produced in the adrenal cortex and gonads. Some
examples are cortisol, testosterone and oestradiol.
4. Amines – Are derived from tyrosine. Examples are
dopamine, adrenaline, thyroxine.
Figure 1 Pathway and pathologies in steroid
biosynthesis.
The hormone levels in the body are regulated through a feedback mechanism loop. Most often this is
a negative feedback mechanism. When a hormone is needed, the production of that hormone will be
stimulated. However, if you reach a point where you have enough of that particular hormone present,
production of that hormone will be inhibited. Another way to regulate hormonal levels could be by a
positive feedback mechanism. In this case, the feedback would increase the production of the hormone
rather than inhibit the production.
The earliest study on endocrinology began with Arnold Berthold in 1984. He discovered that castrated
cockerels did not develop combs and did not exhibit male behaviour. When he replaced the testes back
of the same bird it resulted in normal behaviour and development. Hereafter, he concluded that the testes
secreted a substance that was responsible for the development of the secondary sex characteristics.
Hereby, he concluded that the nervous system did not play a role in this effect.
Another scientist who had a role in understanding endocrinology was Ivan Pavlov. Pavlov investigated
the gastric function of dogs. He removed the oesophagus of dogs and therefore created a fistula. By
adding HCl into the duodenum he observed the reaction of the pancreas, which secreted bicarbonate as
a result. Pavlov believed that the aforementioned result was due to the nervous system. However,
William Bayliss and Ernest Starling proved that Pavlov was wrong in 1902. They performed an
experiment similar to Pavlov’s in which they removed all nervous connections and instilled acid into
the duodenum. This caused the pancreas to secrete. They observed the same response after injecting an
extract of the jejunum mucosa into the jugular vein. In this case some factor in the mucosa was
responsible. They named this factor/substance “secretin” and the first hormone was therefore
discovered.
3
, There are different ways to visualize and detect hormones. These methods predominantly use the
specificity of antibodies. Immunohistochemistry, immunofluorescence and western blot are three
examples in which antibody specificity is used. Within immunohistochemistry a primary antibody
detects the target antigen. A secondary antibody binds to the primary antibody. Usually the secondary
antibody is conjugated with a detection molecule which can further catalyse a colour producing reaction.
Immunofluorescence is based on the same technique as immunohistochemistry. The only difference
within immunofluorescence is in the detection signal, which is a fluorescent signal. Another technique
is the western blot method. This technique is based on immunochromatography where proteins are
separated into a polyacrylamide gel according to their molecular weight.
4
