Anatomy & Physiology:

Thyroid

Which germ layer is the thyroid gland primarily derived from?

Endoderm

In a healthy adult what is the approximate size of the thyroid gland?

Less than 5 cm

In a healthy adult what is the approximate weight of the thyroid gland?

10-20 grams

In a healthy adult what is the average volume of the thyroid gland on ultrasound scan?

7 to 10 ml (range 3 to 20 ml)

How does thyroid volume differ between men and women?

Greater in men

How does thyroid volume change with increasing age?

Increases with advancing age

How does thyroid volume change with bodyweight?

Increases with bodyweight

How does thyroid volume change with iodine intake?

Deceases with increasing iodine intake

What tissue connects the two lobes of the thyroid gland?

Thyroid isthmus

The thyroid gland lies anterolateral to which structure?

Trachea

The thyroid gland lies immediately inferior (caudal) to which structure?

Larynx

Which 2 structures lie posterior to the thyroid gland?

1) Trachea

2) Oesophagus

Which structure lies lateral to the thyroid gland?

Carotid sheath

The inferior pole of each thyroid lobe lies above what structure?

Thoracic inlet

The thyroid isthmus lies immediately inferior to which structure?

Cricoid

How is the position of the thyroid gland affected by swallowing?

Moves superiorly

List the 2 biologically active hormones of the thyroid gland

1) Thyroxine (T4)

2) Triiodothyronine (T3)

Which element is required for the thyroid hormone production?

Iodine

Which is the more bioactive thyroid hormone?

T4 – approximately x5 fold more active than T3

In what form do the majority of T4 and T3 circulate in serum?

Protein-bound

What form of thyroid hormone do thyroid function tests measure?

Free T4 and free T3 i.e., unbound active form

Approximately what percentage of circulating free T3 is produced by the thyroid gland?

20%

How is the majority of circulating free T3 produced?

Deiodination of T4 external to the thyroid gland – approximately 80% produced in this way

Anatomy & Physiology:

Adrenals

List the 3 zones of the adrenal cortex

1) Zona glomerulosa

2) Zona fasciculata

3) Zona reticularis

Which class of hormone does the zona glomerulosa secrete?

Mineralocorticoids

Which class of hormone does the zona fasciculata secrete?

Glucocorticoids

Which is the most important glucocorticoid hormone?

Cortisol

Which class of hormone does the zona reticularis secrete?

Sex steroids - mainly androgens

Which class of hormone does the adrenal medulla produce and secrete?

Catecholamines

Which amino acid are catecholamines synthesised from?

Tyrosine

In a healthy adult what is the approximate weight of an adrenal gland?

4-6 grams

Which adrenal gland is larger?

Left adrenal is larger than the right

How may pregnancy affect the weight of the adrenals?

Increase in weight by almost 50%

What is the position of the adrenals in relation to the peritoneum

Retroperitoneal

Where in relation to the kidney is the adrenal gland located?

Superior medial aspect of the upper renal pole

What percentage of the adrenal gland volume is composed of the cortex?

Cortex is 80-90%

Medulla is 10-20%

Between which 2 organs/tissue does the right adrenal gland lie?

Liver and diaphragm

Between which 2 organs/tissue does the left adrenal gland lie?

Left kidney and aorta

List the 3 main sources of blood flow to the adrenal glands

1) Superior suprarenal arteries

2) Middle suprarenal artery

3) Inferior suprarenal renal arteries

Anatomy & Physiology:

Hypothalamus & Pituitary

Where in the brain is the pituitary gland located?

In the sella turcica within the sphenoid bone

Approximately what percentage of the healthy adult pituitary gland does the posterior pituitary lobe comprise?

25%

What is the main structure connecting the pituitary gland to the hypothalamus?

Pituitary stalk

Where in relation to the pituitary gland is the optic chiasm located?

Superior to the pituitary gland

How is the size of the pituitary gland normally affected by advancing age?

Decreases in size

How is the size of the pituitary gland normally affected by pregnancy?

Increases – almost doubles in size

Where is corticotrophin releasing hormone (CRH) produced?

Hypothalamus

Where is thyrotrophin-releasing hormone (TRH) produced?

Hypothalamus

Where is adrenocorticotropic hormone (ACTH) produced?

Anterior pituitary gland

Where is follicle stimulating hormone (FSH) produced?

Anterior pituitary gland

Where is luteinising hormone (LH) produced?

Anterior pituitary gland

Where is prolactin produced?

Anterior pituitary gland

Where is oxytocin produced?

Hypothalamus

Where is growth hormone releasing hormone (GHRH) produced?

Hypothalamus

Where is anti-diuretic hormone (ADH), also known as vasopressin produced?

Hypothalamus

Where is thyroid-stimulating hormone (TSH) produced?

Anterior pituitary gland

Where is growth hormone produced?

Anterior pituitary gland

Where is anti-diuretic hormone (ADH), also known as vasopressin stored and secreted?

Posterior pituitary gland

What type of hormone is thyroid-stimulating hormone (TSH)?

Glycoprotein hormone

What type of hormone is prolactin?

Polypeptide hormone

What type of hormone is growth hormone?

Polypeptide hormone

What type of hormone is luteinising hormone (LH)?

Glycoprotein hormone

What type of hormone is follicle stimulating hormone (FSH)?

Glycoprotein hormone

What type of hormone is adrenocorticotropic hormone (ACTH)?

Polypeptide hormone

What compound is the precursor of adrenocorticotropic hormone (ACTH)?

Pro-opiomelanocortin (POMC)

How are prolactin levels affected in pregnancy?

Increased

How are prolactin levels affected in breast-feeding?

Increased

Anatomy & Physiology:

Reproductive

In a healthy adult what is the approximate testicular volume?

15-30 ml

In a healthy adult what is the approximate ovarian volume?

5-10 ml

What is the main oestrogen hormone secreted by the ovary?

Oestradiol

Which cells produce testosterone?

Leydig cells of the testes

In which cells does spermatogenesis take place?

Sertoli cells of the testes

In a healthy adult approximately what percentage of the testes are composed of the seminiferous tubules?

90%

Which hormone triggers ovulation?

Luteinising hormone (LH)

In males at what time of day does testosterone peak?

Early morning, approximately 8 am

Which hormone stimulates the growth of breast tissue?

Oestradiol

What term describes the first menstrual bleed?

Menarche

Which hormone stimulates the growth of ovarian follicles?

Follicle stimulating hormone (FSH)

In males which hormone stimulates testosterone production?

Luteinising hormone (LH)

In males what percentage of total testosterone circulates as free biologically active hormone?

2-4%

In females what percentage of total oestradiol circulates as free biologically active hormone?

2-3%

Which protein binds the majority of both oestradiol and testosterone in the circulation?

Sex hormone-binding globulin (SHBG)

Which is the more potent, testosterone or dihydrotestosterone?

Dihydrotestosterone (DHT)

Which enzyme converts testosterone to dihydrotestosterone?

5-alpha reductase

What term is given to the permanent cessation of menses?

Menopause

How many months of amenorrhoea are required for the recognition of clinical menopause?

12 months

Anatomy & Physiology:

Glucose

List 3 metabolic processes as glucose sources

1) Intestinal absorption of food

2) Glycogenolysis

3) Gluconeogenesis (from carbohydrate, protein and fat metabolism)

Which organ is the main site of gluconeogenesis?

Liver

Once transported into cells in what form is glucose stored?

Glycogen

Which 2 organs/tissue have the highest glycogen content?

1) Liver

2) Muscle

Which enzyme is required for the release of glucose into the circulation?

Glucose-6-phosphatase

Which transporter mediates glucose uptake by skeletal muscle and fat from the circulation?

GLUT4 (glucose transporter type 4)

Which organ produces ketone bodies?

Liver

Which cells of the pancreas produce insulin?

Beta cells in the islets of Langerhans

Which cells of the pancreas produce glucagon?

Alpha cells in the islets of Langerhans

Which cells of the pancreas produce somatostatin?

Delta cells in the islets of Langerhans

What type of hormone is insulin?

Peptide hormone

What compound is the insulin receptor?

Glycoprotein

How many subunits does the insulin receptor comprise?

2 alpha-subunits and 2 beta-subunits

Anatomy & Physiology:

Lipids

List the 5 major serum lipoproteins

1) Chylomicrons

2) Very low-density lipoprotein (VLDL)

3) Intermediate-density lipoprotein (IDL)

4) Low-density lipoprotein (LDL)

5) High-density lipoprotein (HDL)

Which 2 lipoproteins carry triglycerides?

1) Chlyomicrons

2) Very low-density lipoprotein (VLDL)

Which lipids are affected by recent food intake and should ideally be measured in the fasting state?

Triglycerides

Which compound is the substrate for production of all steroid hormones?

Cholesterol

Which enzyme hydrolyses triglycerides into fatty acids?

Lipoprotein lipase

In which organ is the enzyme HMG CoA reductase found?

Liver

What term is given to elevated serum total cholesterol, LDL or triglycerides?

Hyperlipidaemia

What term is given to lipid values associated with disease or greater risk of disease where lipid-altering treatment may be of value?

Dyslipidaemia