Endocrine - Hypothalamus Development

From Embryology

Introduction

Human embryonic hypothalamus (Stage 22)
Adult hypothalamus position

The hypothalamus has a key role in regulating the nearby pituitary and peripheral endocrine organ functions. This neural region therefore is associated with hormonally related behaviour (anger and sexual activity), homeostatic regulation (blood pressure, heart rate, appetite, and temperature) and functions that relate to both (puberty, reproductive cycles, and lactation).

In the early embryo, neuroectoderm of the forebrain (prosenecephalon) primary brain vesicle divides to form two secondary brain vesicles, telencephalon (endbrain, cortex) and diencephalon. From the diencephalon ventro-lateral wall, intermediate zone proliferation generates the primordial hypothalamus. Hypothalamus development also occurs differentially in male and female embryos, described as part of neural sexual dimorphism.

In the adult, large neurosecretory cells of the supraoptic nucleus (SON) and the paraventricular nucleus (PVN) project to the neurohypophysis from the hypothalamus. Other key nuclei within the hypothalamus include the sexually dimorphic nucleus (SDN, intermediate nucleus, INAH-1), suprachiasmatic nucleus (SCN) and tuberal lateral nucleus (NTL).

Endocrine Links: Introduction | BGD Lecture | Science Lecture | Lecture Movie | pineal | hypothalamus‎ | pituitary | thyroid | parathyroid | thymus | pancreas | adrenal | endocrine gonad‎ | endocrine placenta | other tissues | Stage 22 | endocrine abnormalities | Hormones | Category:Endocrine
Historic Embryology - Endocrine  
1903 Islets of Langerhans | 1903 Pig Adrenal | 1904 interstitial Cells | 1908 Pancreas Different Species | 1908 Pituitary | 1908 Pituitary histology | 1911 Rathke's pouch | 1912 Suprarenal Bodies | 1914 Suprarenal Organs | 1915 Pharynx | 1916 Thyroid | 1918 Rabbit Hypophysis | 1920 Adrenal | 1935 Mammalian Hypophysis | 1926 Human Hypophysis | 1927 Adrenal | 1927 Hypophyseal fossa | 1930 Adrenal | 1932 Pineal Gland and Cysts | 1935 Hypophysis | 1935 Pineal | 1937 Pineal | 1935 Parathyroid | 1940 Adrenal | 1941 Thyroid | 1950 Thyroid Parathyroid Thymus | 1957 Adrenal

| Category:Hypothalamus | Lecture - Early Neural Development | Lecture - Late Neural Development | Lecture - Head Development | original page

Some Recent Findings

  • Embryonic gonadotropin-releasing hormone signaling is necessary for maturation of the male reproductive axis.[1] "Surprisingly, genetic ablation (in mice) of GnRHR expressing cells significantly increased the number of GnRH neurons in the anterior hypothalamus, suggesting an unexpected role of GnRH signaling in establishing the size of the GnRH neuronal population.

Hypothalamus Endocrine Axes

HPG Axis

Hypothalamus - Pituitary - Gonad endocrine axis.

XXhpgaxis.jpg This cartoon shows the Hypothalamus - Pituitary - Gonad endocrine axis.

The arrows indicate how each of these endocrine organs interact and regulate each others secretions through endocrine feedback mechanisms.

HPA Axis

Hypothalamus - Pituitary - Adrenal endocrine axis.

HPT Axis

Hypothalamus - Pituitary - Thyroid endocrine axis.

Development Overview

Stage 13 image 061.jpg Stage 22 image 055.jpg Gray0654.jpg
Diencephalon region, shown by optic stalk
(Stage 13)
Late embryonic hypothalamus
(Stage 22)
Early fetal human brain
(3 months, from a model by Wilhelm His)
  • Neuroectoderm - prosenecephalon then diencephalon
  • ventro-lateral wall intermediate zone proliferation
  • Mamillary bodies - form pea-sized swellings ventral wall of hypothalamus

Week 5

Secondary Brain Vesicles - Stage 13

Stage 13 serial labeled images
Stage 13 image 057.jpg Stage 13 image 058.jpg Stage 13 image 059.jpg Stage 13 image 060.jpg Stage 13 image 061.jpg Stage 13 image 062.jpg Stage 13 image 063.jpg
B1L B2L B3L B4L B5L B6L B7L

Week 8

Embryo Brain - Stage 22

Stage 22L serial labeled images
Stage 22 image 050.jpg Stage 22 image 051.jpg Stage 22 image 052.jpg Stage 22 image 053.jpg Stage 22 image 054.jpg Stage 22 image 055.jpg Stage 22 image 056.jpg
A1L A2L A3L A4L A5L A6L A7L
Stage 22 image 057.jpg Stage 22 image 058.jpg Stage 22 image 059.jpg Stage 22 image 060.jpg Stage 22 image 061.jpg Stage 22 image 062.jpg Stage 22 image 063.jpg
B1L B2L B3L B4L B5L B6L B7L

Week 10

Early Fetal Brain

10 Week Fetus head images
Human- fetal week 10 head A.jpg Human- fetal week 10 head B.jpg Human- fetal week 10 head C.jpg Human- fetal week 10 head D.jpg

Adult Hypothalamus Hormones

Secreted hormone Abbreviation Produced by Effect
Thyrotropin-releasing hormone
(Prolactin-releasing hormone)
TRH, TRF, or PRH Parvocellular neurosecretory neurons thyroid-stimulating hormone (TSH) release from anterior pituitary (primarily)
Stimulate prolactin release from anterior pituitary
Dopamine
(Prolactin-inhibiting hormone)
DA or PIH Dopamine neurons of the arcuate nucleus Inhibit prolactin release from anterior pituitary
Growth hormone-releasing hormone GHRH Neuroendocrine neurons of the Arcuate nucleus Growth hormone (GH) release from anterior pituitary
Somatostatin
(growth hormone-inhibiting hormone)
SS, GHIH, or SRIF Neuroendocrine cells of the Periventricular nucleus Growth hormone (GH) release from anterior pituitary
Inhibit Thyroid-stimulating hormone|thyroid-stimulating hormone (TSH) release from anterior pituitary
Gonadotropin-releasing hormone GnRH or LHRH Neuroendocrine cells of the Preoptic area follicle-stimulating hormone (FSH) release from anterior pituitary
Stimulate Luteinizing hormone|luteinizing hormone (LH) release from anterior pituitary
Corticotropin-releasing hormone CRH or CRF Parvocellular neurosecretory neurons adrenocorticotropic hormone (ACTH) release from anterior pituitary
Oxytocin Magnocellular neurosecretory cells Lactation (letdown reflex)
Vasopressin
(antidiuretic hormone)
ADH or AVP Magnocellular neurosecretory neurons Increases water permeability in the distal convoluted tubule and collecting duct of nephrons, thus promoting water reabsorption and increasing blood volume

Hormones - Thyrotrophin releasing hormone (TRH), Corticotrophin releasing hormone (CRH), Arginine vasopressin (AVP), Gonadotrophin releasing hormone (GnRH), Growth hormone releasing hormone (GHRH), Somatostatin, Prolactin relasing factor (PRF), Dopamine


Growth hormone (GH) secretion from the pituitary is controlled in many different ways, including positive/negative regulation of synthesis and release by the hypothalamus. Hypothalamic GH releasing hormone (GHRH) activates and somatostatin suppresses growth hormone synthesis and release.

Hypothalamic Nuclei

Supraoptic Nucleus

(SON) Arginine vasopressin (AVP) and oxytocin (OT) synthesis and released in the posterior pituitary. These 2 hormones differ only in 2 amino acids in positions 3 and 8.

Arginine vasopressin (AVP) peptide hormone (9aa, nonapeptide)

  • synthesized as inactive preprohormone
  • regulates blood volume and pressure acting on the kidney and heart
  • Increased osmolality, due to blood volume reduction, increases AVP secretion.

Oxytocin (OT) peptide hormone (9aa, nonapeptide)

  • mainly produced in hypothalamic magnocellular neurons
  • regulates female reproductive pregnancy-associated changes (stimulation of milk ejection, uterine contractions)
  • acts on one type of OT receptor (OTR)
  • hormone is a non-glycosylated protein undergoes an initial cleavage by the convertase magnolysin (EC 3.4.24.62) to OT-Gly-Lys-Arg (OT-GKR).
  • additional processing produces other OT extended molecules: OT-Gly-Lys (OT-GK) and OT-Gly (OT-G, OT-X).
  • OT-G is converted by an α-amidating enzyme to C-amidated nonapeptide which is released into the circulation
  • may have a role in fetal heart growth[2] and in vascular tone, regrowth and remodeling.[3]

Abnormalities: diabetes insipidus (vasopressin deficiency), syndrome of inappropriate antidiuresis (vasopressin excess)


Links: Birth | Search Bookshelf

Paraventricular Nucleus

Hypothalamus PVN and SCN
Oxytocin receptor pathways

(PVN) Arginine vasopressin (AVP) and oxytocin synthesis and released in the posterior pituitary. These 2 hormones differ only in 2 amino acids in positions 3 and 8.

  • magnocellular neurons
  • parvocellular neurosecretory neurons project axons to the pituitary median eminence
  • interneurons and neurons also project centrally

Arginine vasopressin (AVP) peptide hormone (9aa, nonapeptide)

  • synthesized as inactive preprohormone
  • regulates blood volume and pressure acting on the kidney and heart
  • Increased osmolality, due to blood volume reduction, increases AVP secretion.

Oxytocin (OT) peptide hormone (9aa, nonapeptide)

  • mainly produced in hypothalamic magnocellular neurons
  • regulates female reproductive pregnancy-associated changes
  • central effect on social and other behaviors, release from magnocellular dendrites and axonal projections of parvocellular neurons
  • acts on one type of OT receptor (OTR)
  • hormone is a non-glycosylated protein undergoes an initial cleavage by the convertase magnolysin (EC 3.4.24.62) to OT-Gly-Lys-Arg (OT-GKR).
  • additional processing produces other OT extended molecules: OT-Gly-Lys (OT-GK) and OT-Gly (OT-G, OT-X).
  • OT-G is converted by an α-amidating enzyme to C-amidated nonapeptide which is released into the circulation
  • may have a role in fetal heart growth[4]
Links: Birth | Search Bookshelf

Sexually Dimorphic Nucleus

(SDN, intermediate nucleus, INAH-1)

  • Twice as large in young male adults as in young females.
  • At birth 20% of the adult SDN cell number is present, from then until 2-4 years of age cell numbers increase equally rapidly in both sexes.
  • After this age cell numbers start to decrease in girls, creating the sex difference.

The SCN is the clock of the brain and shows circadian and seasonal fluctuations in vasopressin-expressing cell numbers. (SDN and SCN text modified from: Swaab, 1995)

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Suprachiasmatic Nucleus

Hypothalamus PVN and SCN

(SCN) This nucleus is the clock of the brain and shows circadian and seasonal fluctuations in vasopressin-expressing cell numbers.

Links: Search Bookshelf

Tuberal Lateral Nucleus

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(NTL) This nucleus is involved in feeding behavior and energy metabolism.

References

  1. <pubmed>20805495</pubmed>
  2. <pubmed>15316117</pubmed>
  3. <pubmed>10811917</pubmed>
  4. <pubmed>15316117</pubmed>

Reviews

<pubmed>20626426</pubmed>| PMC2972642

<pubmed>12127306</pubmed>

Articles

<pubmed>20637232</pubmed> <pubmed>20628204</pubmed> <pubmed>15840737</pubmed>

Search PubMed

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Cite this page: Hill, M.A. (2024, March 28) Embryology Endocrine - Hypothalamus Development. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Endocrine_-_Hypothalamus_Development

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© Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G