Detailed summary (or as the course coordinators like to call it: syllabus ) of the elective course endocrinology. This summary includes both a literature list and answers/results of the project 'a hormone and its receptor' that you will do during this course.
Syllabus endocrinology Lisa Verhoeven
Index
• Chapter 1 Histology of endocrine glands – pituitary, adrenal, thyroid and parathyroid
• Chapter 2 Mechanisms of hormone action
• Chapter 3 Immunohistology
• Chapter 4 Hypothalamus-pituitary axes
• Chapter 5 Histology of endocrine glands – pancreas, testis and ovaria
• Chapter 6 Adrenal gland – malfunctioning
• Chapter 7 Hormones and Tumours
• Chapter 8 Endocrinology of the Pancreas and malfunctioning
• Chapter 9 Female reproduction
• Chapter 10 Male reproduction
• Chapter 11 The stress axis
• Chapter 12 Growth hormones
• Chapter 13 RAAS
• Chapter 14 Catecholamines
• Chapter 15 Thyroid gland and thyroid hormones
• Chapter 16 Leptin and obesity
• Chapter 17 Calcitropic hormones and Osteoporosis
• Chapter 18 Endocrinology of the Digestive Tract
• Appendices 1-5
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,Chapter 1 Histology of endocrine glands
Exocrine gland: hormone excreted into blood via exit tube
Endocrine gland: hormone-producing cells close to capillaries → entrance of blood via diffusion
Gland cells are epithelial cells → important function of epithelia in this context:
• Absorption nutrients/gases
➔ Shape depends on function: columnar cells have more cytoplasm than squamous cells,
thus can host more (extended) organelles and chemical processes that take place in the
cytoplasm → shape indicates activity
Pituitary gland
Also known as hypophysis → coupled to hypothalamus
The pituitary gland influences other endocrine glands by the hormones it produces as a response to
environmental (incl. bodily) stimuli
The pituitary glands exists of two different parts:
• Posterior pituitary = pars nervosa = posterior lobe = posterior pituitary gland =
neurohypophysis → dense in axon endings: made of tissue from the diencephalon floor
(brain tissue) during embryonic development
• Anterior pituitary = pars distalis = anterior lobe = anterior pituitary gland = adenohypophysis
→ endocrine cell groups: made of ectoderm of the pharyngeal roof during embryonic
development known as Rathke’s pouch
Separate capillary networks
because: in this way lower quantities of RH/IH have to be produced by hypothalamus, as these reach
the anterior pituitary more efficiently compared to the case in which these networks were fused →
there’s no point in getting hormones to the posterior pituitary → longer distance travelling so more
loss of hormone in that case (waste of energy, inefficient)
Posterior pituitary
Neural cell bodies lie in the hypothalamus of which the axon endings extend into
the posterior pituitary
Along the axon length, hormones are produced → transported and stored into axon
endings → released in fast response to stimuli
• Hormones released in capillary network surrounding the axon endings
Two hormones are produced in the hypothalamus by neuroendocrine cells in
supraoptic and paraventricular nuclei in that enter the blood via the posterior
pituitary:
• Oxytocin: peptide hormone, receptors → cell uterus wall: initiate labour
→ myoepithelial cells in milk gland tubes: milk ejection
• ADH (antidiuretic hormone): also known as vasopressin, peptide hormone
Receptors → kidney distal tubular cells: stimulates water resorption from urine → decreased
urine release alcohol blocks ADH release, antagonistic function of RAAS (chapter 13)
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, Anterior pituitary
Contains two capillary networks with portal veins in between → surround endocrine cells
Fenestrated capillaries: fenestrae allow hormones from hypothalamus to exit the capillaries so they
reach endocrine cells for stimulation and hormones produced by endocrine cells enter the capillaries
for blood transport to target cells → diffusion downstream concentration gradient driven
Hypothalamus produces two kinds of hormones that act on the endocrine cells in the anterior
pituitary:
• Release hormones: stimulate hormone release
- CRH: corticotropin-releasing hormone
- GnRH: gonadotropin-releasing hormone
- TRH: thyrotropin-releasing hormone
- GHRH: growth hormone-releasing hormone
• Inhibitory hormones: opposite
- GHIH (somatostatin): inhibits GH and TSH release
- PIH: inhibits prolactin (PRL) release
Endocrine cells can be divided in two categories based on what stain they bind
• Basophilic cells: bind basic (blue) stain → acidic hormone content: ACTH, TSH, FSH, LH, MSH
• Acidophilic cells: bind acidic (red) stain → basic hormone content: GH, PRL
• Chromophobes: cells that don’t stain → because they have released hormone content
Staining category Cell Hormone(s) Function(s)
Stimulates body growth and regulates metabolism
acidophilic Somatotrophs hGH (human growth hormone)
TSH stimulates thyroid gland to secrete its hormones
basophilic Thyrotrophs TSH (thyroid stimulating hormone)
Men: sperm production by testes
Basophilic Gonadotrophs FSH (follicular stimulating hormone) Woman stimulates production of oocytes and secretion of
oestrogens by ovaries
Men: stimulates secretion of testosterone from testes
LH (luteinising hormone) Woman: stimulates oestrogens secretion by ovaries,
ovulation, formation of corpus luteum, and secretion of
progesterone by corpus luteum
Initiates milk production in suitably prepared mammary
acidophilic Lactotrophs PRL (prolactin) glands, uterus muscle contraction to start labour
Adrenal glands
The pituitary produces ACTH that via the blood reaches the adrenal glands → located on
top of the kidneys: rich in fatty acids (hormone precursor storage), high blood supply
(efficient hormone signalling). Adrenal glands two layers as a gross ultrastructure:
• Cortex: outer layer → responsive to ACTH → slow stress hormones
• Medulla: inner layer → responsive to neuronal stimuli → fast stress hormones
Cortex
The cortex produces corticoids which are steroid hormones → cortex contains three
subzones that all respond to ACTH:
• Zona glomerulosa: responsive to ACTH and angiotensin II → cells lie in circular
groups
- Produce mineralo-corticoids (aldosterone): influence mineral
homeostasis/metabolism (chapter 13)
• Zona fasciculata: middle layer → long cords of cells that have a cholesterol rich
cytoplasm so nicknamed spongiocytes → fenestrated capillaries
- Cholesterol → precursor for gluco-corticoids (cortisol): glucose/lipid
metabolism
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