Endocrine

What are the major classes of hormones?

Peptide/protein hormones, steroid hormones, and amine hormones.

How are peptide hormones synthesized and transported?

Synthesized as preprohormones → processed in ER and Golgi → stored in vesicles; transported freely in plasma.

How are steroid hormones synthesized and transported?

Derived from cholesterol; synthesized on demand; transported bound to carrier proteins.

How are amine hormones synthesized and transported?

Derived from tyrosine; catecholamines are stored and circulate freely; thyroid hormones are bound to plasma proteins.

What types of receptors do peptide hormones bind?

Membrane-bound receptors (GPCRs, tyrosine kinase receptors); activate second messenger systems.

What types of receptors do steroid hormones bind?

Intracellular receptors; act as transcription factors to regulate gene expression.

What types of receptors do amine hormones bind?

Catecholamines bind membrane receptors; thyroid hormones bind nuclear receptors.

What are examples of peptide hormones?

Insulin, glucagon, growth hormone, ACTH, TSH.

What are examples of steroid hormones?

Cortisol, aldosterone, estrogen, progesterone, testosterone.

What are examples of amine hormones? (think catecholamines)

Epinephrine, norepinephrine, dopamine (catecholamines); T3 and T4 (thyroid hormones).

How do water-soluble hormones travel in the bloodstream?

They circulate freely without carrier proteins and bind to membrane-bound receptors.

How do lipid-soluble hormones travel in the bloodstream?

They require carrier proteins (e.g., albumin, TBG) and bind to intracellular or nuclear receptors.

What types of membrane-bound hormone receptors exist?

G-protein coupled receptors (GPCRs), receptor tyrosine kinases, cytokine receptors.

What second messengers are commonly activated by GPCRs?

cAMP, IP₃/DAG, calcium ions.

What is the mechanism of steroid hormone action?

Bind intracellular receptors → hormone-receptor complex enters nucleus → binds DNA → alters transcription.

What is the role of the hypothalamus in endocrine regulation?

Integrates neural signals and secretes releasing/inhibiting hormones into hypophyseal portal system to regulate anterior pituitary.

What is the embryologic origin of the anterior pituitary?

Oral ectoderm (Rathke’s pouch); forms glandular tissue.

What is the embryologic origin of the posterior pituitary?

Neuroectoderm from diencephalon; forms neural tissue.

What hormones are secreted by the anterior pituitary? (FLAT PEG)

ACTH, TSH, GH, LH, FSH, Prolactin, MelanocyteSH

What hormones are secreted by the posterior pituitary?

Oxytocin and vasopressin (ADH); synthesized in hypothalamus and released from posterior pituitary.

What is the difference between anterior and posterior pituitary secretion?

Anterior pituitary is glandular and regulated by hypothalamic hormones; posterior pituitary releases neurohormones from hypothalamic axons.

What are the hypothalamic hormones that regulate the anterior pituitary? (Do Thy Some Growth Gonad Co)

TRH(thyrotropin), CRH(corticotropin), GnRH, GHRH, somatostatin (inhibits GH), dopamine (inhibits prolactin).

What is an example of negative feedback?

T3/T4 inhibit TRH and TSH secretion.

What is an example of a short-loop negative feedback?

Pituitary hormone inhibits hypothalamic releasing hormone (e.g., TSH inhibiting TRH).

What is an example of a long-loop negative feedback?

Peripheral hormone inhibits both pituitary and hypothalamic hormones (e.g., T3/T4 inhibiting TSH and TRH). so inhibits both the organ and the on/off switch

What is the hypothalamic-pituitary-thyroid axis?

Hypothalamus releases TRH → anterior pituitary releases TSH → thyroid releases T3 and T4 → negative feedback to TRH and TSH.

What is the function of TRH?

Stimulates TSH and prolactin release from anterior pituitary.

What is the function of TSH?

Stimulates thyroid follicular cells to produce and release T3 and T4.

What is the function of T3 and T4?

Increase basal metabolic rate, enhance protein synthesis, stimulate growth and development, increase β-adrenergic sensitivity.

What is the difference between T3 and T4?

T3 is more potent and biologically active; T4 is more abundant and converted to T3 in peripheral tissues.

What are symptoms of hyperthyroidism?

Weight loss, heat intolerance, tachycardia, anxiety, tremor, goiter.

What are symptoms of Graves disease? Cause?

Autoimmune hyperthyroidism; symptoms include weight loss, heat intolerance, tachycardia, exophthalmos(bulging eyes), goiter,. Cause= excessive production of T3/T4 due to damage to negative feedback system(see inc in T3/T4 but dec in TSH)

What are symptoms of hypothyroidism?

Weight gain, cold intolerance, bradycardia, fatigue, constipation, dry skin.

What are symptoms of Hashimoto thyroiditis? Cause?

Autoimmune hypothyroidism; symptoms include fatigue, cold intolerance, weight gain, dry skin, bradycardia. Cause= antithryoid antibody gradually destroys thyroid tissue leading to low T3/T4 and high TSH==>Priamry hypofunction

What is the function of calcitonin?

Secreted by parafollicular cells of thyroid; lowers blood calcium by inhibiting osteoclasts.

What stimulates calcitonin secretion?

High serum calcium; acts as a counter-regulatory hormone to PTH.

What is the function of parathyroid hormone (PTH)?

Secreted by chief cells of parathyroid; increases blood calcium by stimulating osteoclasts, increasing renal reabsorption, and activating vitamin D.

What stimulates PTH secretion?

Low serum calcium; inhibited by high calcium and active vitamin D.

How does vitamin D affect calcium and phosphate levels?

Increases intestinal absorption of both calcium and phosphate; promotes bone mineralization.

What is the role of vitamin D in calcium homeostasis?

Enhances intestinal absorption of calcium and phosphate; activated by PTH.

What is the role of the anterior pituitary in endocrine regulation?

Receives hypothalamic signals via portal system; secretes tropic hormones that regulate peripheral endocrine glands.

What is the role of the posterior pituitary in endocrine regulation?

Stores and releases oxytocin and vasopressin synthesized in hypothalamic neurons.

What is the function of oxytocin?

Stimulates uterine contractions during labor and milk ejection during lactation.

Adrenal cortex releases____ after being stimulated by____

Cortisol, aldosterone, androgens; ACTH

Adrenal medulla releases___ after being stimulated by___

Epi and Norepi; ACH

Primary hyper/hypo function vs Secondary hyper/hypo function

Primary= problem with organ; Secondary= problem with releasing/stimulating hormone

What are the carriers of thyroid hormone?

Thyroxine-binding globulin(TBG, carries the most T3 and T4); transthyretin; Albumin(not great binding but there is a lot of it)

What is used to make thyroid hormone? What happens if we are deficient?

Iodine; hyperthyroidism because thyroid enlarges to compensate 

What do C Cells make? What do follicular cells make?

Calcitonin; Follicular cells produce and secrete T3 and T4

What is calcitriol?

active form of vitamin D; increases blood Ca levels