Lecture 13: Hypothalamus and Pituitary Gland Flashcards

This set of flashcards covers the vocabulary and key concepts regarding the anatomy, histology, hormone functions, and clinical disorders of the hypothalamus and pituitary gland based on the lecture notes.

Endocrine System Functions

Development (proliferation, growth, differentiation, organogenesis), Reproduction, Metabolism, and Homeostasis (water/salt balance, blood volume/pressure).

Hormones

Messenger molecules that bind to specific receptors to alter target cell structure or activity, such as stimulating $DNA$ synthesis or modifying enzymes.

Hypothalamus

An area at the base of the brain where neurons send axons to form the posterior pituitary and release neurohormones into portal vessels to control the anterior pituitary.

Posterior Pituitary

A neuroendocrine organ of neuronal developmental origin (down-growth from the diencephalon) that releases oxytocin and vasopressin ($ADH$).

Anterior Pituitary

A gland of ectodermal origin (up-growth from Rathke’s pouch) that secretes $GH$, $FSH$, $LH$, $ACTH$, $TSH$, and prolactin.

Oxytocin

A hormone involved in parturition (uterine contractions), the milk ejection reflex, and maternal behavior; regulated by a positive feedback loop.

Vasopressin ($ADH$)

Also known as antidiuretic hormone, it is one of the two main hormones released by the posterior pituitary.

Median Eminence

The site where hypothalamic neurons release neuropeptide hormones into portal vessels to reach the anterior pituitary.

Chromophobes, Acidophils, and Basophils

The three cell types identified in the anterior pituitary through Haematoxylin and Eosin (H & E) staining.

Growth Hormone Releasing Hormone ($GHRH$)

A hypothalamic releasing hormone that stimulates the production of Growth Hormone ($GH$).

Corticotropin Releasing Hormone ($CRH$)

A hypothalamic releasing hormone that stimulates the production of Adrenocorticotrophic Hormone ($ACTH$).

Thyrotropin-releasing Hormone ($TRH$)

A hypothalamic releasing hormone that stimulates the production of Thyroid Stimulating Hormone ($TSH$).

Gonadotropin Releasing Hormone ($GnRH$)

A hypothalamic releasing hormone that stimulates the production of $LH$ and $FSH$.

Somatostatin ($SS$)

A hypothalamic inhibiting hormone that suppresses the release of $GH$ and $TSH$.

Dopamine ($DA$)

A hypothalamic inhibiting factor that suppresses the release of Prolactin ($PRL$).

Luteinising Hormone ($LH$) and Follicle-Stimulating Hormone ($FSH$)

Hormones made in gonadotrophs that control the production of oestrogen, progesterone, and testosterone.

Growth Hormone ($GH$)

A hormone made in somatotrophs that has direct anabolic effects and stimulates the liver to produce insulin-like growth factor-1 ($IGF-1$).

Pituitary Dwarfism

A condition characterized by proportionately shorter stature caused by the failure of growth hormone secretion or action.

Achondroplasia

The most common form of dwarfism, caused by an $FGFR$ mutation leading to abnormal bone growth rather than $GH$ deficiency.

Gigantism

A condition resulting from the hypersecretion of $GH$ throughout childhood.

Acromegaly

A condition caused by $GH$ over-secretion (usually from a pituitary adenoma) after bones have fused, causing growth in the hands, feet, and jaws.

Thyroid Stimulating Hormone ($TSH$)

A hormone made in thyrotrophs that acts on the thyroid to generate $T_3$ (triiodothyronine) and $T_4$ (thyroxine).

Toxic Goitre

A condition of hyperthyroidism characterized by an enlarged thyroid and Exophthalmos (bulging eyes).

Prolactin ($PRL$)

A hormone made in mammotrophs that stimulates lactation; its oversecretion can lead to gynecomastia in males and loss of reproductive function.

Adrenocorticotropic Hormone ($ACTH$)

A hormone made in corticotrophs that stimulates the adrenal cortex to produce steroid hormones regulating sodium, blood pressure, and stress response.

Cushing’s Syndrome

A disorder caused by excess adrenal steroids (cortisol), leading to obesity of the face and trunk, hirsutism, and skin discoloration.

Negative Feedback Control

A homeostatic loop where the response to a hormone reduces the original stimulus; examples include long-loop feedback from $IGF-1$ or cortisol.

Short-loop Negative Feedback

A process where a trophic hormone from the anterior pituitary feeds back directly to the hypothalamus to inhibit releasing hormones.