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AKA hypophysis cerebri
2 Lobes: Anterior and Posterior Lobes
Derived from different tissues embryonically (💡as a result, have different functions)
Pituitary stalk (infundibulum - DIFFERENT FROM TEETH) connects to hypothalamus
Direct connection between hypothalamus and posterior pituitary
Hypophysectomy = removal of the pituitary (💡"-ectomy" = removal of body part)
Anterior Lobe
Anterior Lobe
AKA adenohypophysis, pars distalis
Glandular (💡“adeno” = "gland")
Makes LH, FSH, Prolactin, ACTH, TSH, GH
Different cell types make different hormones:
Basophils make: Corticotropes, Gonadotropes, Thyrotropes
Acidophils make: Somatotropes, Lactotropes
Chromophobes
Part of hypothalamo-hypophyseal portal system
Hypothalamo-Hypophyseal Portal System
Hypothalamo-Hypophyseal Portal System
Indirectly connects hypothalamus and anterior pituitary
Regulation of LH and FSH production by GnRH
Axons from GnRH neurons in the tonic and surge centers of the hypothalamus terminate on blood vessels of the Primary Portal Plexus (PPP)
GnRH made by neurons in the hypothalamus enters the blood and is transported by the Portal Vessels (PV) to the Secondary Portal Plexus (SPP) in the anterior pituitary
GnRH diffuses into anterior pituitary, where it stimulates gonadotroph cells in the anterior pituitary to release LH and FSH
LH and FSH enter the circulation of the SPP and leave the anterior pituitary via the Hypophyseal Vein (HV)
Image credit: Greene Xue
Hormones Produced by Anterior Lobe
Hormones Produced by Anterior Lobe
All are proteinaceous (have a gene that codes for them)
Growth Hormone (GH)/ Somatotropin
Thyroid-Stimulating Hormone (TSH)
Prolactin (PRL)
Adrenocorticotropic hormone (ACTH)
Luteinizing Hormone (LH)
Follicle-Stimulating Hormone (FSH)
Growth Hormone (GH)/Somatotropin
Growth Hormone (GH)/Somatotropin
Reduces protein breakdown and use of glucose for energy
Increases mobilization of fatty acids from adipose
Growth-promoting effects are mediated by somatomedins
Insulin-like growth factor (IGF)
Levels are highest in young, growing animals
Simulated by: GHRH, reduced blood glucose (starvation)
Inhibited by: GHIH, somatomedins
Recombinant bovine growth hormone (rBGH/ rBST)
Increases food efficiency and lactation
Human GH and bovine GH are different proteins
Thyroid Stimulating Hormone (TSH)
Thyroid Stimulating Hormone (TSH)
Stimulates production and release of thyroid hormones
Thyroxine (T4)
Triiodothyronine (T3)
Stimulated by: TRH
Inhibited by: T3, T4 (negative feedback loop)
Prolactin (PRL)
Prolactin (PRL)
Stimulates growth of the mammary gland and milk production after parturition (birth)
Regulates maternal behaviors
Stimulated by: PRF, estrogen, suckling
Inhibited by: Dopamine
Adrenocorticotropic Hormone (ACTH)
Adrenocorticotropic Hormone (ACTH)
Stimulates development and function of Adrenal Cortex
Stimulates glucocorticoid production by adrenal gland
Stimulated by: CRH
Inhibited by: glucocorticoids
The Gonadotropins: LH and FSH
The Gonadotropins: LH and FSH
Gonadotropins stimulate the gonads: regulate gonadal hormone production and gametogenesis
Luteinizing Hormone (LH)
Stimulates production of testosterone
Regulates ovarian follicle development and spermatogenesis
Induces ovulation and corpus luteum formation in females (💡Luteinizing Hormone stimulates Corpus Luteum)
Target cells of ovary/testis: Theca Cells/ Leydig Cells
Follicle-Stimulating Hormone (FSH)
Simulates production of estrogen, inhibin, androgen-binding protein
Regulates ovarian follicle development and spermatogenesis
Target cells of ovary/testis: Granulosa cells/ Sertoli Cells
Test Yourself:
Test Yourself:
Q: What does the Hypothalamo-hypophyseal portal system indirectly connect?
Q: What does the Hypothalamo-hypophyseal portal system indirectly connect?
A: Hypothalamus and Anterior Pituitary
Q: What are the functions of Growth Hormone (GH)/Somatotropin?
Q: What are the functions of Growth Hormone (GH)/Somatotropin?
A:
Reduces protein breakdown and use of glucose for energy
Increases mobilization of fatty acids from adipose
Q: What hormones does Thyroid Stimulating Hormone (TSH) stimulate the production and release of?
Q: What hormones does Thyroid Stimulating Hormone (TSH) stimulate the production and release of?
Q: What are the functions of Prolactin (PRL)?
Q: What are the functions of Prolactin (PRL)?
A:
Stimulates growth of the mammary gland and milk production after parturition (birth)
Regulates maternal behaviors
Q: What is the main function of Adrenocorticotropic Hormone (ACTH)?
Q: What is the main function of Adrenocorticotropic Hormone (ACTH)?
Stimulates development and function of Adrenal Cortex
Q: What do Gonadotropins (LH and FSH) regulate?
Q: What do Gonadotropins (LH and FSH) regulate?
A: Regulate gonadal hormone production and gametogenesis
Posterior Lobe
Posterior Lobe
AKA neurohypophysis, pars nervosa
Nervous tissue (💡nervous system = “neuro”)
Axons from the Paraventricular Nucleus (PVN) and Supraoptic nucleus (SON) in the hypothalamus directly terminate on blood vessels in the posterior pituitary
Oxytocin and ADH enter blood in posterior lobe
No portal system (direct connection)
Image credit: Greene Xue
Hormones Produced by Posterior Lobe
Hormones Produced by Posterior Lobe
All are proteinaceous (have a gene that codes for them)
Oxytocin
Antidiuretic Hormone (ADH)
Oxytocin
Oxytocin
Produced by Hypothalamus (PVN) and released by posterior pituitary
Stimulates muscle contractions
Positive feedback loops
Mammary Gland: Milk Letdown/Ejection
Uterus: contractions during parturition
Antidiuretic Hormone (ADH)
Antidiuretic Hormone (ADH)
Produced by Hypothalamus (SON) and released by posterior pituitary
Constricts blood vessels (vasopressin - 💡"press" on blood vessels) to increase BP
Increases aquaporins in the collecting ducts and increased permeability to H2O
Water is re-absorbed into bloodstream
Urine becomes more concentrated
Negative feedback
Secreted in response to increased blood osmolality or decrease in BP
Water is retained and blood osmolality decreases
ADH release stops
Alcohol 🥂🍷🍸🍹🍾 inhibits ADH release
Test Yourself:
Test Yourself:
Q: What is the main function of oxytocin?
Q: What is the main function of oxytocin?
A: Stimulates muscle contractions
Q: Explain the negative feedback loop of Anti-diuretic Hormone (ADH)
Q: Explain the negative feedback loop of Anti-diuretic Hormone (ADH)
A:
ADH secreted in response to increased blood osmolality or decrease in BP
Water is retained and blood osmolality decreases
ADH release stops
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