426 Unit 4 | Common Illnesses or Disorders in Childhood and Home Care
hormones to the master gland (pituitary gland). These include: ● Thyroid-releasing hormone ● Corticotropin-releasing hormone (CRH) ● Luteinizing hormone (LH)–releasing hormone or gonadotro- pin-releasing hormone (GnRH) ● Growth hormone (GH)–releasing hormone ● Somatostatin—stimulates the pituitary gland to stop the release of GH Pituitary Gland (Hypophysis) Also called the master gland, the pituitary gland is located beneath the hypothalamus in the base of the brain. This gland controls other glands through stimulating hormones or inhibi- tory factors that turn the target glands on or off (Ilie, 2020). The pituitary gland has two main lobes: ● The anterior lobe (adenohypophysis) secretes the following (Ilie, 2020): ● GH—stimulates growth of cells; stimulates protein synthesis and prevents protein breakdown ● Thyroid-stimulating hormone (TSH)—stimulates the thy- roid glands to make thyroid hormones ● Adrenocorticotrophic hormone (ACTH)—stimulates the cortex of the adrenal glands to make glucocorticoids and sex steroids ● Prolactin—stimulates milk production in the mammary glands of females ● Follicle-stimulating hormone (FSH)—stimulates the ova- ries to develop eggs within the follicles of the ovaries ● LH—stimulates the follicles in the ovaries to rupture and release the egg and corpus luteum production in females; stimulates testosterone production in males ● Melanocyte-stimulating hormone—stimulates melanin synthesis and release from skin and hair ● The posterior lobe (neurohypophysis) secretes the following: ● Antidiuretic hormone (ADH) (vasopressin)—stimulates the kidneys to absorb and conserve water, increasing blood volume ● Oxytocin (Pitocin)—stimulates smooth muscle contrac- tion, milk letdown reflex, and the expulsion of the fetus and placenta Pineal Body ● Located in the middle of the brain ● Stimulated by light exposure through the optic nerve ● Secretes the hormone melatonin, which helps with the regula- tion of wake–sleep cycles and circadian rhythms (Brashers & Huether, 2020). Thymus ● Located in the anterior ventral aspect of the chest at the base of the heart ● Atrophies with age ● Secretes thymosin that stimulates the development of T cells (Brashers & McCance, 2020).
The Endocrine System
Pineal gland
Hypothalamus
Pituitary gland
Thyroid gland
Parathyroid glands
Thymus
Adrenal glands
Pancreas
Testes
Ovaries
FIGURE 181 The endocrine system.
–
–
Hypothalamus
Releasing hormone
+
Short-loop feedback
–
Anterior pituitary
Pituitary hormone
+
Target gland
Target gland hormone
FIGURE 182 Feedback system from the pituitary to the target glands.
Hypothalamus Located at the base of the brain, the hypothalamus sends messages from the autonomic nervous system to the tar- get organs (Ilie, 2020) by secreting releasing or inhibitory
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