Which hormone is most abundant?

T4

Parathyroid glands are:

Pea sized glands located on the posterior thyroid

Parathyroid glands can be:

Ectopic in about 10-20% of the population

Blood supply to the parathyroid

Inferior thyroid arteries, drain into thyroid veins & lymphatics

Parathyroid is adjacent to

Right and left recurrent laryngeal nerves

If parathyroid tumor develops

This can push on laryngeal nerve

Pressure on laryngeal nerve can cause

voice changes and difficulty swallowing

PTH is synthesized in

Chief cells

Parathyroid glands produce

PTH

PTH regulates

Ca++ in extracellular fluids

Most calcium is found

bound to albumin

When we measure calcium, we measure

Calcium bound to albumin

If albumin lab value is low this can also alter:

Calcium levels

In addition to calcium, PTH also regulates

Phosphoprous and vitamin D

Calcium thermostat is another name for

Parathyroid gland

CaSR is

calcium-sensing receptors

Where are CaSR found?

Outside of parathyroid cells

Bone response to PTH

Osteoclasts accelerate the erosion of bone matrix.

Kidney response to PTH

Increases production of calcitrol

Calcitrol

Acts to increase renal absorption of calcium

Where do kidneys reabsorb calcium?

distal convoluted tubule

Gut response to PTH

Calcitrol stimulates calcium absorption in the intestines

Cholesterol in our skin cells react to

UV light to start the process of Vitamin D production

1,25 hydroxy vitamin D means

Carbons at 1 and 25, hydroxylated

PTH summary of functions

Activates & increases osteoclasts to free calcium
Increases renal tubular reabsorption of ca++
Increases renal excretion of phosphate
Increases conversion of vitamin D to active form
Increases intestinal calcium absorption indirectly by increasing active form of vitamin D

1,25 hydroxy vitamin D

Normal storage form of Vit D

Active Vit D

2,25 hydroxylated vitamin D

25 hydroxy vitamin D becomes hydroxylated (OH) again to become

2,25 hydroxylated vitamin D, the active form

Calcitonin

is polypeptide hormone secreted by parafollicular C-cells within the medulla of the thyroid gland

calcitonin opposes the actions of

PTH

calcitonin is the anti

PTH

Calcitonin is secreted in respnse to

increased calcium levels

calcitonin acts by

inhibiting bone resorption by inhibiting osteoclasts

BMP

Basic metabolic panel

CMP

comprehensive metabolic panel

Ca++ in the blood levels:

~8.5-10.5mg/dL

Vitamin D is a

Prohormone

Vitamin D is needed for

Calcium homeostasis

Vitamin D absorption

Bone resorption
Kidney excretion
Gut absorption

Which osteocyte is involved in the proliferation of new bone?

Osteoblasts

Calcitonin is produced in

Medulla of thyroid

What type of cells produce PTH

Chief cells

Parathyroid conditions

Hypo
Hyper
Hypercalcemia
Osteoporosis

HypoPTHism causes

-Most common in people with thyroid surgically removed
-Genetic abnormal gland development (DiGeorge syndrome)
-Autoimmune
-Metabolic
-PTH resistance
-Drug induced

Glucagon, heparin, and lasix can all cause

Hypoparathyroidism

HypoPTHism

Inadequate PTH, low calcium
Low calcium -> High phosphate and low VIT D
Low VIT D -> reduced CA++ absorption in gut -> Break down of ca++ from bones

Low magnesium can also lower

calcium

Low magnesium can cause

hypoparathyroidism

Primary hyperparathyroidism

due to excessive PTH production and secretion at the PTH gland

Primary hyperparathyroidsim can also be caused by

Reduced PTH supression by elevated ca++

Primary hyperPTHism

shifts the threshold on the thermostat

What hormones oppose PTH

Calcitonin

Most common cause of primary hyperPTHism

genetics

Hypercalcemia

too much calcium

Hypercalcemia symptoms

Increase in bones, stones, grones and psychiatric overtones

Abnormal bone remodeling caused bhy

hypercalcemia

increase in kidney stones caused by

hypercaclemia

Too much calcium in digestive tract causes

abdominal cramping, nausea, constipation

Lethargy, depressed mood, psychosis, cognitive dysfunction are all caused by

hypercalcemia

hypercalcemia effect on brain

psychiatric overtones

hypercalcemia effect on abdomen

groans

hypercalcemia effect on bones

abnormal, bizarre bone growth/remodeling and fracture risk

kidney stones

hypercalcemia

hypercalcemia defined as:

>10.5 with normal albumin

Primary hyperparathyroidism presentation

Elevated PTH, low phos, shortened QT

Most common 2 HyperPTHism

kidney disease

kidney disease causes

hypocalcemia, hyperphosphatemia due to decreased calcitrol

increased PTH in 2 hyperPTHism is a

positive feedback loop

excessive PTH, secondary, due to chronic kidney disease

cannot absorb calcium in kidneys, cannot absorb calcium in GI, which causes increase in PTH

Elevated PTH but low calcium

most common diagnostic for secondary hyperPTH

Primary vs secondary hyperPTHism

Primary, high ca++
Secondary, low ca++

Osteoporosis

State of low bone mass with microarchitectural deterioration of bone structure, strength, fragility

Max peak bone mass depends on

nutrition, physical activity, general health, hormones

Peak bone mass in your

thirties

Msost important factor is gonadal steroid deficiency

estrogen
testosterone

Osteomalacia

Soft/weak bones

Most common cause of osteomalacia

vitamin D deficiency