HUBS191 Lecture 26 Endocrine 2 Flashcards

Flashcards for HUBS191 Lecture 26 Endocrine 2

Pituitary Gland

Located in the fossa of the sella turcica of the sphenoid bone at the base of the brain; plays important roles in growth, development, metabolism, and homeostasis.

Hypothalamus

Secretes its own hormones that control pituitary function.

Anterior Pituitary (Adenohypothesis)

Derived from epithelial tissue, accounting for about 75% of the pituitary gland; includes the pars distalis and pars tuberalis.

Posterior Pituitary (Neurohypothesis)

Derived from neuroectoderm, mainly composed of pituicytes; includes the pars nervosa and infundibulum.

Pars Intermedius

Lies between the anterior and posterior lobes and may produce melanocyte stimulating hormone (MSH).

Hypothalamic-Hypophyseal Portal System

Releasing hormones (RH) and release inhibiting hormones (RIH) secreted from hypothalamic neurons diffuse into a 1st capillary network, then portal veins carry RH/RIH to a 2nd capillary network in the anterior pituitary, stimulating or inhibiting hormone secretion.

ADH and Oxytocin

Neurosecretory cells in the supraoptic (SON) and paraventricular nuclei (PVN) of the hypothalamus produce these hormones.

Stimuli for Oxytocin Release

Stretching of the cervix during childbirth and infant suckling during breastfeeding.

Antidiuretic Hormone (ADH)

Posterior pituitary hormone that increases water reabsorption in the kidneys and constricts arterioles at higher doses.

Stimulus for ADH Release

Increased Extracellular Fluid (ECF) osmolarity.

Neurogenic Diabetes Insipidus

Insufficient ADH secretion, often due to trauma or injury, leading to large volumes of dilute urine.

Nephrogenic Diabetes Insipidus

Kidneys not responding to ADH, can be genetic, medication induced, or secondary to renal disease.

Syndrome of Inappropriate ADH Secretion (SIADH)

Inappropriate release of ADH, potentially caused by drugs like MDMA, leading to overhydration, hyponatremia, and cerebral edema.

Control of Anterior Pituitary Hormone Secretion

Releasing or inhibiting hormones from the hypothalamus.

Thyrotropin-releasing hormone (TRH)

Releases thyroid stimulating hormone (TSH).

Corticotropin-releasing hormone (CRH)

Releases adrenocorticotropin (ACTH).

Growth hormone-releasing hormone (GHRH)

Releases growth hormone (GH).

Growth hormone inhibitory hormone (GHIH) aka somatostatin

Inhibits growth hormone (GH) release.

Gonadotrophin releasing hormone (GnRH)

Releases luteinizing hormone (LH) and Follicle stimulating hormone (FSH).

Prolactin inhibitory hormone (PIH) = dopamine

Inhibits prolactin (PRL) release.

Human Growth Hormone (hGH)

Protein hormone secreted by somatotrophs which promotes the increased size and number of cells, particularly muscle, bone, and cartilage.

Somatomedins (Insulin-like Growth Factors / IGFs)

Proteins formed by the liver in response to hGH, mediating growth hormone's effects, like Insulin-like Growth Factor-1 (IGF-1).

Factors that Stimulate GHRH and GH Release

Deep sleep, low blood glucose, strenuous exercise, fasting, trauma, stress, testosterone, and estrogen.

Factors that Reduce GH Secretion

Increased blood glucose, increased fatty acids in the blood, increased somatomedins in blood, and aging.

Dwarfism

Lack of GH during childhood.

Gigantism

Excess GH prior to closure of epiphyseal plates.

Acromegaly

Excess GH secretion after epiphyseal plates fuse, leading to increased muscle, bone, and organ mass.

Acromegaly Features

Large hands, thickened frontal bone, kyphosis, large tongue and mandible, arthritis, carpal tunnel syndrome, enlarged heart, high BP, hyperglycemia, and visual disturbances.