Endocrine system: Hormones

Growth Hormone (GH)

Location: produced by somatrophs, secreted by anterior pituitary

Functions: promotes protein synthesis and encourages use of fats for fuel, mobilizes fat, elevates blood glucose by decreasing uptake and encouraging glycogen breakdown(anti-insulin). stimulates the liver to produce-like growth factors (IGFs)

How: targets mainly bone and skeletal muscle, epiphyseal plates. Growth hormone releasing hormone (GHRH)- daily cycle, deep sleep, hypoglycemia, low fatty acids, stressors

Inhibitors: Growth hormone inhibiting hormone (GHIH)- somatostatin, inhibits GH release, hyperglycemia, obesity, increases GHIH or decreases GHRH

Hypersecretion: in children can cause gigantism because GH targets growing epiphyseal plates. in adults acromegaly= enlarged extremities, tumor in anterior pituitary

Hyposecretion: in adults not a big deal, in children slows down bone growth. Pituitary dwarfism=when caught before puberty normal bone growth can be initiated. Associated with other anterior pituitary hormone deficiencies

Thyroid Stimulating Hormone (TSH)- thyrotropin

Location: produced by the thyrotrophs in anterior pituitary

Function: stimulates the normal development and secretory activity of the thyroid

How: stimulated by the thyrotropin releasing hormone (TRH)

Inhibitors: rising blood levels of the thyroid hormones that act on the pituitary and hypothalamus. GHIH

Adrenocorticotropic hormone (ACTH)

Location: Secreted by corticotrophs in anterior pituitary

Function: Stimulates the adrenal cortex to release corticosteriods and glucocorticosteriods, resist stressors

How: Triggers by the hypothalamic corticotropin releasing hormone (CRH)- daily rhythms (peaks in morning)

Inhibitors :Rising glucocorticoid levels inhibit CRH and ACTH secretion, maintaining balance. fever, hypoglycemia, stress

Hypersecretion: excess glucocorticosterioids =, ACTH pituitary releasing tumor, cushings syndrome

Hyposecretion: weight loss, low plasma glucose, high potassium levels, addisons disease

Gonadotropins; follicle stimulating hormone (FSH) and luteinizing hormone (LH)

Location: in the anterior pituitary, ovaries and testes

Function: regulate function of the gonads. FSH-production of gametes. LH-production of gonadal hormones, testosterone is males and in females triggers ovulation and ovarian hormones

How: release is controlled by the GnRH, gonadotropin releasing hormone from the hypothalamus

Inhibitors: supressed by gonadal hormones (feedback)

Prolactin (PRL)

Location: produced by prolactin cells in the anterior pituitary

Function: stimulate milk production in the breasts

How: release is controlled by inhibitory hormones (PIH)-dopamine. estrogen can trigger release

Inhibitors: decrease of PIH

Oxytocin

Location: paraventricular neurons in the hypothalamus, stored and released into blood by posterior pituitary.

Function: Childbirth and lactation, stimulates the contraction of the uterus to progress labor and promotes milk ejection. “cuddle hormone”.

How: Also acts as the 2nd messenger to mobilize Calcium. positive feedback. from the posterior pituitary via action potentials

Inhibited: lack of neural stimulus

Antidiuretic Hormone (ADH)

Location: released by the posterior pituitary gland in response to signals from the hypothalamus. kidneys

Function: inhibits urine formation to retain water, water reabsorption back into the bloodstream. during blood loss- can cause high blood pressure

How: hypothalamus monitors solutes in the blood by osmoreceptors, transmit impulses to release ADH. can also be triggered by pain, low blood pressure, certain drugs. Hypothalamus action potentials

Inhibited: drinking lots of water, alcohol

Deficiency: Diabetes insipidus, lots of urine output, intense thirst

Hypersecretion: neurosurgery, trauma, cancer. SIADH, retention of fluid, headaches, brain edema