Hormones and Human Development

Osteoporosis Vulnerability

• Women are more prone to osteoporosis than men on average
• Women stop producing IGF-1 in their 5th decade, whereas men continue to produce it

IGF-1 Similarity

• IGF-1 is structurally similar to somatostatin

Orchestration of Linear Bone Growth

• Growth hormone is synthesized/secreted from the pituitary gland and is necessary, but not sufficient, for orchestrating linear bone growth

Calcium Malabsorption

• Calcium malabsorption in children, often due to vitamin D deficiency, can lead to rickets

Hormone Synthesis

• Thyroid hormone requires the amino acid tyrosine and the element iodine for its synthesis

Human Growth Regulation

• Human growth depends on many hormones and corresponding receptors
• The synthesis of these hormones and receptors relies on genes
• These genes encode the hormones or enzymes that catalyze their formation, so human growth is polygenic

Humerus Stabilization

• Rotator cuff injury can affect up to 4 muscles that stabilize the head of the humerus in the glenoid cavities
• These muscles are the subscapularis, supraspinatus, infraspinatus, and teres minor

Blood Calcium Levels

• The receptors and controllers of the negative feedback diminish a downward signal of blood calcium levels back to ~9mg/dl
• These reside within the hormone-secreting cells of the parathyroid gland

Cortisol Characteristics

• Cortisol is a steroid hormone synthesized and secreted from the adrenal cortex in response to stress
• Cortisol inhibits epiphyseal growth plate activity, which can stunt linear bone growth during growing years

Osteoclast Stimulation

• Parathyroid hormone and calcitriol stimulate osteoclasts

Patient Diagnosis

• Scurvy should be considered for a patient with a history of economic insecurity, alcoholism, poor diet lacking fruits/vegetables/supplements, losing teeth, gum bleeding, and subcutaneous bleeding

Vitamin D Deficiency

• Lack of vitamin D, from sunlight or diet (cholecalciferol/calcidiol), can cause osteomalacia in adults and rickets in children

Cholesterol-Derived Hormones

• Calcitriol, testosterone, estrogen, and cortisol are derived from cholesterol (all steroid hormones)

Dwarfism

• Achondroplasia, a type of dwarfism, typically has no medical treatment, except for limb lengthening surgery in some cases

Post-Growth Facial Changes

• Acromegaly, caused by a pituitary adenoma that synthesizes high amounts of growth hormone, is shown as the gradual increase in the size of cartilaginous structures of the face, accompanied by increased prominence of the forehead and lower jaw after linear bone growth stops

Epiphyseal Plate Dwarfism

• Achondroplastic dwarfism is a type of dwarfism where epiphyseal plates have markedly diminished growth rates
• This results in dramatically shortened long bones of the appendicular skeleton, while flat bones of the skull maintain relatively normal growth

Vitamin D Synthesis Progression

• The correct progression of molecular synthesis leading to mature fully functional vitamin D is 7-dehydrocholesterol, cholecalciferol, calcidiol, calcitriol

Epiphyseal Growth Plate Activity

• Testosterone and estrogen initially promote epiphyseal growth plate activity, then promote the diminishment of epiphyseal growth plate activity, ultimately ending in epiphyseal plate closure and the appearance of the epiphyseal line

Thyroid Hormone Functions

• Thyroid hormone regulates basal metabolic rate
• It drives essential brain growth/development early in life (infancy, toddlerhood)
• It supports the function of the GH-IGF-1 axis

Osteoporosis Treatments

• Calcidiol and calcitonin, aside from estrogen/SERMs, can be used to treat osteoporosis

Calcitriol Synthesis

• The synthesis of calcitriol requires the skin, liver, and kidney working in tandem
• This requires the ordered action of the skin, followed by the liver, and then the kidney

Osteoporosis Management

• Taking calcium and vitamin D supplements alone is often insufficient for managing osteoporosis
• This fails to address gaps in activity between osteoclasts and osteoblasts, where osteoclast activity predominates, and abnormal SERM secretion by osteocytes

Muscle Appearance on Cadavers

• During cadaver dissection, parallel threads or strings comprising the muscle can be noticed, and these are muscle cells or muscle fibers (same structure), or fascicles

Vitamin D3

• Vitamin D3 is cholecalciferol synthesized by the skin upon exposure to ultraviolet light from the sun

GH-IGF-1 Targets

• The ultimate final hormonal target of the GH-IGF-1 is the epiphyseal growth plates of long bones

Hormone Completion

• Calcitriol cannot undergo its final completion without stimulation from parathyroid hormone

Gigantism and Acromegaly Characteristics

• Gigantism and acromegaly can occur independently depending on the age of onset of the causative pituitary adenoma
• They often occur simultaneously with a disturbance in vision
• Can be treated safely surgically and medically

Commonality of Dwarfism Types

• Cretinism, pituitary dwarfism, and achondroplasia can lead to a dramatically shortened stature

Joints and Fluid

• Synovial and diarthrotic joints contain a joint capsule and a joint cavity with fluid similar to serous fluid

Head Joints

• Sutures and gomphoses are located exclusively in structures within the head

Birth Canal Joints

• Thick sutures present at birth, referred to as fontanelles, and the pubic symphysis of the mother, facilitate the passing of the baby’s head through the birth canal

Fibrous Joints

• Sutures, syndesmoses, and gomphoses are fibrous joints

Tooth Layer

• The outermost layer of teeth, comprised largely of hydroxyapatite, is enamel

Synchondroses Characteristics

• Synchondroses include joints between an epiphysis and the metaphysis/diaphysis of a juvenile bone
• They can mature into synostoses by a certain age
• They are all synarthrotic