Questions and Answers
Steroid hormones are synthesized 'as needed'.
True
Steroid hormones are synthesized from _____
cholesterol
What are the sources of cholesterol for steroid hormone synthesis?
Dietary fat or can be synthesized de novo from acetyl CoA.
What are the steroid hormones?
Signup and view all the answers
What tissues are steroidogenic?
Signup and view all the answers
Cholesterol can be synthesized in ______ or be taken up via ____
Signup and view all the answers
What are the 2 regulated steps in cholesterol uptake in steroid hormone synthesis?
Signup and view all the answers
What are 2 inherited disorders of cholesterol transport?
Signup and view all the answers
What is the mutation in Wolman disease?
Signup and view all the answers
What is the mutation in congenital lipoid adrenal hyperplasia?
Signup and view all the answers
What are the functions of P450SCC in steroid hormone synthesis?
Signup and view all the answers
What is required to convert cholesterol to pregnenolone?
Signup and view all the answers
What are the locations and functions of StAR protein and CYP11A1?
Signup and view all the answers
What hormones are produced from the different locations in the adrenal glands?
Signup and view all the answers
How are different products produced from the medulla and different zones in the cortex?
Signup and view all the answers
How is ACTH produced and where is it produced from?
Signup and view all the answers
What is the effect of ACTH activation?
Signup and view all the answers
How is gene expression of cortisol synthesis regulated?
Signup and view all the answers
The conversion of pregnenolone to 11-deoxycortisol occurs in the __________. 11-deoxycortisol is converted to cortisol in the __________.
Signup and view all the answers
Glucocorticoid receptor (GR) is an (intra/extracellular) receptor.
Signup and view all the answers
Study Notes
Overview of Steroid Hormones
- Steroid hormones are synthesized "as needed," unlike peptide hormones which are pre-synthesized.
- They play critical roles in metabolism, osmotic balance, differentiation, and reproduction.
Synthesis of Steroid Hormones
- Steroid hormones are synthesized from cholesterol.
- Cholesterol sources include dietary fats or synthesis via acetyl CoA.
- Key steroid hormones: progesterone, cortisol, aldosterone, testosterone, and estradiol.
Steroidogenic Tissues
- Primary tissues involved in steroid hormone synthesis: adrenal glands, gonads, and placenta.
- Initial steps in steroid synthesis are identical across different tissues.
Cholesterol Uptake and Regulation
- Cholesterol can be synthesized in the body or obtained from food.
- Key regulated steps involve:
- StAR protein transporting cholesterol into the mitochondria.
- P450SCC enzyme converting cholesterol to pregnenolone, the rate-limiting step.
Genetic Disorders Affecting Steroid Synthesis
- Wolman disease: mutation in lysosomal acid lipase (LAL), leading to cholesterol accumulation and organ failure.
- Congenital lipoid adrenal hyperplasia: mutation in StAR causing hormone deficiencies and impaired steroid synthesis.
P450SCC Function
- Catalyzes hydroxylations and cleavage to convert cholesterol into pregnenolone.
- Recognized as the rate-limiting step in steroid hormone synthesis, requiring oxygen and NADPH.
StAR Protein and CYP11A1 Locations
- StAR protein is found in the outer mitochondrial membrane (OMM) facilitating cholesterol import.
- CYP11A1 (P450SCC) is located in the inner mitochondrial membrane (IMM) for pregnenolone conversion.
Adrenal Gland Hormones
- Adrenal medulla produces catecholamines (tyrosine derivatives).
- Adrenal cortex divides into three zones:
- Glomerulosa: produces aldosterone
- Fasciculata: produces cortisol
- Reticularis: produces DHEA
Activation and Regulation of ACTH
- ACTH is produced in response to stress; hypothalamus releases corticotropin-releasing hormone (CRH) into portal circulation.
- ACTH stimulates steroidogenesis in the adrenal cortex, promoting cortisol release.
Effects of ACTH Activation
- Activates protein kinase A (PKA), leading to:
- Stimulation of cholesterol transfer and increased availability.
- Activation of StAR and CYP11A1 enzymes.
- Enhanced fat particle uptake.
Gene Expression Regulation in Steroid Synthesis
- ACTH regulates cortisol synthesis through cAMP response elements in gene promoters.
Conversion Pathway of Steroids
- Pregnenolone is converted to 11-deoxycortisol in the cytoplasm, with further conversion to cortisol occurring in mitochondria.
Receptor Information
- Glucocorticoid receptor (GR) functions as an intracellular receptor, mediating the effects of glucocorticoids like cortisol.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Description
Test your knowledge on steroid hormone synthesis with these flashcards. Learn how steroid hormones are made as needed and their sources, focusing on cholesterol. Perfect for students studying endocrinology or related fields.