Steroid hormones such as cortisol and testosterone are all synthesized from the lipid cholesterol.
Missing Word
cholesterol
Cholesterol is the lipid precursor of every steroid hormone. Because steroids are built from it, they are lipid soluble and can cross the plasma membrane.
Category: Hormone Basics
Question 2
Inside a target cell, the enzyme phosphodiesterase breaks down cyclic AMP, ending the signal started by a water-soluble hormone.
Missing Word
phosphodiesterase
Phosphodiesterase is the enzyme that inactivates cyclic AMP by converting it to AMP. Because cyclic AMP is broken down quickly, the response to a water-soluble hormone stops soon after the hormone is no longer bound to its receptor.
Category: Hormone Basics
Question 3
The pituitary gland hangs from the base of the brain by a stalk called the infundibulum.
Missing Word
infundibulum
The infundibulum is the stalk that connects the pituitary gland to the brain above it. Axons to the posterior pituitary and the portal vessels to the anterior pituitary both pass through it.
Category: Pituitary and Hypothalamus
Question 4
Releasing and inhibiting hormones that control the anterior pituitary are produced by the region of the diencephalon called the hypothalamus.
Missing Word
hypothalamus
The hypothalamus is the part of the diencephalon that links the nervous and endocrine systems. Its releasing and inhibiting hormones travel through portal vessels to regulate the anterior pituitary.
Category: Pituitary and Hypothalamus
Question 5
Inside each follicle of the butterfly-shaped gland in the neck, T3 and T4 are stored attached to a large glycoprotein called thyroglobulin, which fills the colloid.
Missing Word
thyroglobulin
Thyroglobulin is the glycoprotein made by follicular cells and stored in the colloid. Iodine is attached to its tyrosine residues, and T3 and T4 are cleaved from it before release.
Category: Thyroid and Parathyroid
Question 6
An enlarged thyroid gland, which can result from a lack of dietary iodine, is called a goiter.
Missing Word
goiter
A goiter is an enlargement of the thyroid gland. With too little iodine, thyroid hormone levels fall, TSH rises through reduced negative feedback, and the gland grows.
Category: Thyroid and Parathyroid
Question 7
Low blood levels of the ion calcium are the main stimulus for release of parathyroid hormone.
Missing Word
calcium
Calcium is the ion parathyroid hormone regulates. When blood calcium falls, the parathyroid glands release their hormone, which raises calcium through effects on bone, kidneys and intestine.
Category: Thyroid and Parathyroid
Question 8
Cortisol raises blood glucose in part by stimulating gluconeogenesis, the synthesis of new glucose from noncarbohydrate sources such as amino acids.
Missing Word
gluconeogenesis
Gluconeogenesis is the production of new glucose from sources such as amino acids and glycerol, mainly in the liver. Cortisol promotes it during long-term stress to keep blood glucose available.
Category: Adrenal Glands
Question 9
When blood sugar falls, alpha cells of the pancreatic islets release the hormone glucagon.
Missing Word
glucagon
Glucagon is the alpha cell hormone that raises blood glucose by promoting glycogen breakdown and glucose production in the liver. It opposes the action of insulin.
Category: Pancreatic Islets
Question 10
Delta cells of the pancreatic islets secrete somatostatin, which inhibits the release of the other islet hormones.
Missing Word
somatostatin
Somatostatin is the delta cell hormone of the pancreas. It acts locally to inhibit insulin and glucagon secretion, and the same hormone made by the hypothalamus inhibits growth hormone release.
Category: Pancreatic Islets
Question 11
The hormone leptin, released by adipose tissue, signals satiety to the brain and reduces appetite.
Missing Word
leptin
Leptin is a hormone secreted by fat cells in proportion to fat stores. It acts on the hypothalamus to produce a feeling of fullness and lower food intake.
Category: Other Endocrine Tissues
Question 12
A gland in the mediastinum secretes hormones called thymosins that support the development of T lymphocytes.
Missing Word
thymosins
Thymosins are hormones of the thymus, which lies in the mediastinum. They promote the development and maturation of T lymphocytes, the cells of adaptive immunity.
Category: Other Endocrine Tissues
Question 13
Sertoli cells of the testes and granulosa cells of the ovaries secrete inhibin, a hormone that suppresses FSH release.
Missing Word
inhibin
Inhibin is a gonadal hormone that provides negative feedback to the anterior pituitary, reducing follicle-stimulating hormone secretion. This helps regulate sperm production and follicle development.
Category: Other Endocrine Tissues
Question 14
The gonads and the adrenal cortex, which secrete steroid hormones, develop from the embryonic germ layer called mesoderm.
Missing Word
mesoderm
Mesoderm is the middle embryonic germ layer, and the steroid-producing glands arise from it. Endocrine glands that arise from ectoderm and endoderm, such as the pituitary, thyroid and pancreatic islets, produce amine, peptide and protein hormones instead.
Category: Development and Aging
Question 15
Declining ovarian secretion of estrogen and progesterone leads to menopause, the end of a woman's reproductive years.
Missing Word
menopause
Menopause is the permanent end of menstrual cycles and fertility. It occurs as the aging ovaries shrink, respond less to gonadotropins and produce less estrogen and progesterone.
Category: Development and Aging