Introduction to Endocrinology

Flashcards covering key principles of endocrinology, hormone regulation, fetal development, metabolism, drug interactions, and endocrine system disorders based on Dr. Raheleh Ahangari's lecture notes.

What negative feedback mechanism regulates the secretion of thyroid-stimulating hormone (TSH) in the hypothalamus-pituitary-thyroid axis?

Thyroxine provides negative feedback inhibition, which decreases the responsiveness of the anterior pituitary to stimulation by thyrotropin-releasing hormone (TRH).

What embryonic developmental failure can lead to an "ectopic thyroid" gland that functions poorly and causes cretinism?

The failure of the thyroid gland to descend during embryonic development from its origin at the base of the tongue to its usual site in the lower anterior neck.

What clinical characteristics define neonatal hypothyroidism (cretinism)?

Neonatal hypothyroidism is characterized by poor feeding, sexual retardation, mental retardation, and retardation of bone growth.

What skeletal disorder is depicted, characterized by disproportionate dwarfism with short limbs, trident hands, marked lordosis, and frontal/parietal bossing?

Achondroplasia

In the nephron diagram provided, which tubule segment is furosemide-sensitive and transports $\text{Na}^+\text{K}^+2\text{Cl}^-$?

The thick ascending limb.

According to the provided overview diagram of endocrine dysfunction, what are two main gland-level causes of endocrine hyperfunction?

Tumor and hyperplasia.

What is atrial natriuretic peptide (ANP), and how does it lower blood volume?

ANP is a 28-amino-acid polypeptide produced by the atria of the heart in response to stretching from increased blood volume. It functions as an endogenous diuretic by prompting the kidneys to excrete more salt and water.

How does insulin facilitate increased glucose uptake by target cells?

Insulin promotes the redistribution of glucose transporters to the plasma membrane.

What is the function of osteoprotegerin in maintaining bone health?

Osteoprotegerin is a soluble TNF receptor family member that blocks the actions of TNF-related proteins in bone cells, protecting against the onset of osteoporosis.

How do the effects of estrogens on bone matrix differ from those of glucocorticoids and thyroid hormones?

Estrogens promote the accrual of bone matrix and prevent osteoporosis, whereas glucocorticoids and thyroid hormones promote bone loss.

How does progesterone contribute to maintaining pregnancy in humans?

Progesterone decreases myometrial sensitivity to oxytocin, leading to the suppression of uterine contractile function.

What functions does leptin perform in the human body?

Leptin is secreted from adipose tissue to control satiety in the central nervous system and promote maturation of the reproductive tract, triggering the onset of puberty.

How is the maternal immune system altered during pregnancy to prevent rejection of the fetus?

Pregnancy tends to suppress the cellular immune response while leaving the humoral immune response intact.

What selective actions and clinical risks are associated with Tamoxifen and Raloxifene?

Both drugs exhibit estrogen-like effects on bone while inhibiting estrogen action in breast tissue. However, Tamoxifen increases the risk of uterine cancer, and both exacerbate hot flashes and increase the risk of blood clots and strokes.

Why can treating hypothyroidism with thyroid hormone precipitate latent adrenal insufficiency?

Thyroid hormone increases cortisol metabolism, which can exceed the capacity of an endocrine system with insufficient adrenal reserve.

What genetic enzyme deficiency causes defective cortisol production in 21-hydroxylase deficiency syndrome?

Defect in the gene encoding the 21-hydroxylase enzyme.

What non-endocrine tumor products exemplify ectopic hormone production causing endocrine hyperfunction?

Ectopic production of ACTH, ADH, and calcitonin.

What clinical features characterize Syndrome X (metabolic syndrome)?

Syndrome X is characterized by excessive insulin resistance (overlapping into type 2 diabetes mellitus), hyperlipidemia with increased triglycerides and cholesterol, and hypertension.

What specific central nervous system abnormalities are associated with severe hypothyroidism, glucocorticoid excess, and insulin excess?

Severe hypothyroidism can cause depressed mental status progressing to coma; glucocorticoid excess can cause psychosis; insulin excess causes hypoglycemia leading to coma.