202 ES - Biochemistry Flashcards by Ina Vong

Hormonal regulation of pituitary gland is primarily ______ feedback

negative

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Polyuria

Excretion of large volume of dilute urine

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Central vs nephrogenic DI

Central: deficiened ADH
Nephrogenic: ADH normal but renal resistance

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Polydipsia

Abnormal great thirst

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The majority of hypothyroidism cases are?

Primary causes

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3 types of primary hypothyroidism

Iatrogenic - drugs/radiotherapy
Autoimmune - chronic autoimmune thyroiditis
Other - postpartum thyroiditis

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Patients of chronic autoimmune thyroiditis (Hashimoto’s thyroiditis) have ______ levels of thyroid peroxidase (TPO) & thyroglobulin (Tg) antibodies

high

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Causes of iatrogenic hypothyroidism

Amiodarone

Lithium

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TSH & fT4 levels of primary, subclinical, secondary/tertiary hypothyroidism

Primary - ↑ TSH, ↓ fT4
Subclinical - ↑ TSH, normal fT4
Secondary/tertiary - normal/↓ TSH, ↓ fT4

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Hyperthyroidism more commonly affects which gender?

Women

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Most common cause of hyperthyroidism

Grave’s disease

- autoimmune disorder involving the production of autoantibodies against TSH receptor

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Toxic multinodular goitre

2nd most common cause of hyperthyroidism

Caused by iodine deficiency

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TSH & fT4 levels of primary, subclinical, pituitary adenoma hyperthyroidism

Primary - ↓ TSH, ↑ fT4
Subclinical - ↓ TSH, normal fT4
Secondary/tertiary (Pituitary adenoma) - ↑ TSH, ↑ fT4

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4 stages of nonthyroidal illness

Low T3
High T4
Low T4
Recovery

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Physiological functions of calcium (6)

Bone formation
Brain function & neurotransmission
Heart function
Muscle function
Blood clotting
Cellular metabolism

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______ dissolve bone;

______ form new bone.

Osteoclast; Osteoblast

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Where is intracellular calcium stored?

Endoplasmic reticulum (ER)
Sarcoplasmic reticulum (SR)
Mitochondria

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Factors affecting blood Ca2+

Changes in plasma protein concentration
Changes in anion concentration
Acid-base abnormality

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Causes of hypercalcemia

Hyperparathyroidism
Malignancy
Vitamin D intoxication
Medication-induction

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Causes of hypocalcemia

Hypoalbuminemia
Hypoparathyroidism
Poor intake or impaired absorption of calcium
Vitamin D deficiency/low calcitriol
Liver & renal diseases
Osteoblastic metastases

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Hypothalamus-pituitary-adrenal gland (HPA) axis regulates?

Cortisol

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Renin-angiotensin system regulates?

Aldosterone

The sympathetic system regulates?

Hormones secreted from adrenal medulla

Adrenal gland disorders of too much hormones

Cushing’s syndrome
Congenital adrenal hyperplasia
Pituitary tumor
Hyperaldosteronism

Adrenal gland disorders of too little hormones

Addison's disease

Diagnostic strategies of adrenal hormone disorders - Suspected hypofunction - Suspected hyperfunction

Suspected hypofunction - Stimulation test | Suspected hyperfunction - Suppression test

What is Addison's disease?

Long-term disorder Insufficient production of all steroid hormones Lack of aldosterone & cortisol

Presentation of gluocorticoid (cortisol) insufficiency (Addison's disease)

Weight loss & long-fasting fatique Weakness & malaise Low bp

Androgen insufficiency (Addison's disease) - male - female

``` Male: do not express signs of ↓ androgens Female: - ↓ body hairs - reduced libido - hot flushes ```

Presentation of mineralcorticods (aldosterone) insufficiency (Addison's disease)

Hypotension Hyponatremia & hyperkalemia Shock

Clinical features of Addison's disease

Pigmentation - bc excess ACTH - sun-exposed & pressured areas Knuckles, elbow, knees, palmar creases

Diagnostic strategy for Addison's disease (3 stages)

1. Demonstration of inappropriately low cortisol level 2. Determination the level of adrenal dysfunction (primary vs secondary) 3. Identification of specific cause of adrenal insufficiency

In Addison's disease: | Cortisol levels are ______; ACTH levels are ______

low; high

Presentation: | Cushing's vs Addison's

Cushing's: - hypotension - hypernatremia - weight gain - hair overgrowth Addison's: - hypotension - hyponatremia - weight loss - hair loss

Diagnostic strategy for Cushing's disease (2 stages)

1. Confirmation of raised blood cortisol | 2. To establish cause of observed cortisol excesss

Normal fasting blood sugar level?

72 - 99 mg/dL

How is glucose transported into the cell?

Na+ & ATP-independent transporter Na+ & ATP-dependent transporter - glucose cannot diffuse into cell directly - once inside cell, glucose phosphorylated to G6P and cannot leave cell

Na+ & ATP-independent transporter

GLUT1-GLUT14 Facilitated transport, uniporter

Low Km, ______ affinity; | High Km, ______ affinity

high; low

Na+ & ATP-dependent transporter

SGLT1 SGLT2 on epithelial cells of intestine, renal tubules, choroid plexus Secondary active transport, energy required, symporter

Which 3 hormone regulates blood sugar?

Glucagon - ↑ blood glucose Insulin - ↓ blood glucose Stress hormones (epinephrine) - "fight or flight"

Synthesis of insulin

Preproinsulin (ER) → proinsulin (Golgi apparatus) → insulin + C-peptide (stored in secretory vesicles)

How is insulin secretion regulated? - high blood glucose - low blood glucose

High blood glucose: ATP ↑ → K+ efflux ↓ → hyperpolarization↓ → Ca2+ influx ↑ → insulin release ↑ Low blood glucose: ATP ↓ → K+ efflux ↑ → hyperpolarization↑ → Ca2+ influx ↓ → insulin release ↓

How is insulin degraded?

Insulinase (found in liver & kidney)

Insulin effect on glucose transporters

Insulin ↑ glucose transport into insulin-sensitive cells - GLUT4

GLUT4 mechanism

1. Insulin binds to receptor 2. Signal transduction cascade 3. Exocytosis 4. Glucose enters cell

Insulin effect on carbohydrate metabolism

Stimulation - Glucose uptake by cells through GLUT4 - glycogenesis Inhibit - glycogenolysis - gluconeogenesis

Insulin effect on fat metabolism

Stimulation - transport of FA into adipose tissue - conversion of excess glucose into FA - synthesis of FA & TAG Inhibit - FA release from adipose tissue - ketogenesis

Insulin effect on protein metabolism

Stimulation - a.a. entry to cells - protein synthesis (translation) Inhibit - protein catabolism & a.a. release from cells - gluconeogenesis

What depends on insulin for glucose uptake?

GLUT4 | - found in muscle & adipose

Type 1 DM

Deficiency of insulin - destruction of β cells in islets of Langerhans by T-cells & autoantibodies - insulin-dependent DM

Type 2 DM

Insulin resistance - failure of insulin receptors to response - body unable to use insulin - non-insulin-dependent DM

Insulinoma

High secretion of insulin due to β cell tumor | - associated with type 2 DM

rT3 in nonthyroidal illness & hypothyroidism

Nonthyroidal illness: rT3 ↑ | Hypothyroidism: rT3 ↓