Endocrine System

Growth Hormone Disorders

Disorder GHRH GH IGF-1
Laron syndrome ↓ (1°)
Hypopituitarism ↓ (1°)
Acromegaly ↑ (1°)

Growth Hormone Stimulation Tests

  • Insulin
  • Glucagon
  • Arginine
  • Clonidine
  • Propranolol

Medications for Acromegaly

Mechanism Medication
Somatostatin agonists Octreotide
Lanreotide
GH antagonists Pegvisomant
D2 agonists Bromocriptine
Cabergoline

Treatment of Hyperprolactinemia

Mechanism Medication Indications
D2 agonists Bromocriptine Hyperprolactinemia
  Cabergoline Hyperprolactinemia

Thyroid Hormone Synthesis

Step Enzyme
Oxidation Thyroperoxidase (TPO)
Organification Thyroperoxidase (TPO)
Coupling Thyroperoxidase (TPO)
Deiodination 5'-deiodinase

Thyroid Hormone Disorders

Disorder TRH TSH TH
Subclinical hypothyroidism -
1° Hypothyroidism ↓ (1°)
2° Hypothyroidism ↓ (1°)
Subclinical hyperthyroidism -
Struma ovarii ↑ (1°)
1° Hyperthyroidism ↑ (1°)
2° Hyperthyroidism ↑ (1°)

Presentation of Hypothyroidism {WAS-TIRED}

  • Weight gain
  • Ataxia
  • Short stature
  • Tired
  • Intolerance to cold
  • Reflex delayed
  • Edema :: myxedema
  • Dry skin

Presentation of Congenital Hypothyroidism

  • Developmental delay
  • Failure to thrive
  • Large anterior fontanelle
  • Coarse facies
  • Macroglossia
  • Umbilical hernia

Presentation of Hyperthyroidism {SWEATING}

  • Sweating
  • Weight loss
  • Emotional lability
  • Edema :: pretibial myxedema
  • ↑ Appetite
  • Tremor
  • Tachycardia
  • Intolerance to heat
  • Nervousness
  • Goiter

Workup of 1° Hyperthyroidism

Cause RAI Thyroglobulin
Graves disease
Multinodular goiter -
Toxic adenoma -
Thyroiditis
Exogenous TH

Treatment of Hyperthyroidism

  • Thyroid peroxidase inhibitors
    • Propylthiouracil
    • Methimazole
    • Iodine [Lugol] solution
  • Deiodinase inhibitors
    • Propylthiouracil
    • Propranolol
    • Corticosteroids
  • β antagonists :: Propranolol
  • Radioiodine ablation
  • Surgery

Parathyroidism Hormone Disorders

Disorder PTH Ca P Bone Disorder
1° Hypoparathyroidism ↓ (1°) -
PTH-independent hypercalcemia ↑ (1°) ↑/↓ (1°) -
1° Hyperparathyroidism ↑ (1°) Osteitis fibrosa cystica
2° Hyperparathyroidism ↓ (1°) ↑ (1°) Renal osteodystrophy
3° Hyperparathyroidism Renal osteodystrophy
Vitamin D deficiency ↓ (1°) ↓ (1°) Rickets
Osteomalacia
Pseudohypoparathyroidism (PHP) ↓ (1°) ↑ (1°) Albright hereditary osteodystrophy
Familial hypocalciuric hypercalcemia (FHH) -

Presentation of Hyperparathyroidism

  • Stones
  • Renal stones
  • Bones
  • Brown tumor
  • Osteitis fibrosa cystica
  • Groans
  • Constipation
  • Psychiatric overtones
  • Depression

Congenital Adrenal Hyperplasia

Deficiency Mineralocorticoid Glucocorticoid Androgen BP
21-Hydroxylase
11-Hydroxylase
17-Hydroxylase

Mineralocorticoid Disorders

Disorder Renin Mineralocorticoid Na & BP
Hypertension ↑ (1°)
Waterhouse-Friderichsen syndrome ↓ (1°)
CAH :: 21-Hydroxylase deficiency ↓ (1°)
CAH :: 11-Hydroxylase deficiency ↑ (1°)
CAH :: 17-Hydroxylase deficiency ↑ (1°)
Conn syndrome ↑ (1°)
Adrenal tumor ↑ (1°)
Exogenous steroid ↑ (1°)
Renin-secreting tumor ↑ (1°)
Hypotension ↓ (1°)

Glucocorticoid Disorders

Disorder CRH ACTH Glucocorticoid
Congenital adrenal hyperplasia (CAH) ↓ (1°)
Addison disease ↓ (1°)
Waterhouse-Friderichsen syndrome ↓ (1°)
Hypopituitarism ↓ (1°)
Exogenous steroid ↑ (1°)
Adrenal tumor ↑ (1°)
Ectopic ACTH ↑ (1°)
Cushing disease ↑ (1°)

Diagnosis of Cushing Syndrome

  • 24-hour urine cortisol
  • Dexamethasone suppression test :: low-dose
  • Midnight salivary cortisol
  • Midnight serum cortisol

Sex Hormone Disorders

Disorder GnRH LH & FSH SH
Klinefelter syndrome ↓ (1°)
Turner syndrome ↓ (1°)
Menopause [Ovarian failure] ↓ (1°)
Resistant ovary [Savage] syndrome ↓ (1°)
Hypopituitarism ↓ (1°)
Kallmann syndrome ↓ (1°)
Hypothyroidism ↓ (1°)
Hyperprolactinemia ↓ (1°)
Pregnancy ↑ (1°)
Germ cell tumor ↑ (1°)
Exogenous steroid ↑ (1°)
Androgen insensitive syndrome (AIS)
Polycystic ovary syndrome (PCOS) ↑/↓ ↑/↓ ↓/↑

ADH Disorders

Diagnosis ADH Osmolarity
Polydipsia ↓ (1°)
Central DI ↓ (1°)
Nephrogenic DI ↑ (1°)
SIADH ↑ (1°)

Etiology of Nephrogenic Diabetes Insipidus (DI)

  • Mutations
    • Vasopressin receptor
    • Aquaporin
  • Electrolyte disturbances
    • Hypercalcemia
    • Hypokalemia
  • Hematologic disorders
    • Sickle cell disease
    • Multiple myeloma
  • Autoimmune diseases
    • Sjogren syndrome
    • Sarcoidosis
  • Amyloidosis
  • Drugs
    • Lithium
    • Demeclocycline

Medications for Nephrogenic Diabetes Insipidus (DI)

  • NSAIDs :: Indomethacin
  • Thiazides :: Hydrochlorothiazide

Etiology of Syndrome of Inappropriate Secretion of ADH (SIADH)

  • Malignancies :: small cell carcinoma
  • CNS disorders
  • Pulmonary diseases
    • Tuberculosis
    • Pneumonia
  • Drugs
    • Carbamazepine
    • Cyclophosphamide
    • SSRIs

Treatment of Syndrome of Inappropriate Secretion of ADH (SIADH)

  • Fluid restriction
  • V2 antagonists :: -Vaptans
  • Nephrogenic DI-inducing drugs
    • Lithium
    • Demeclocycline

Insulin Disorders

Disorder Insulin Glucose
Starvation ↓ (1°)
DM type 1 ↓ (1°)
DM type 2 ↑ (1°)
Insulinoma ↑ (1°)

Presentation of Glucagonoma {4D}

  • Depression
  • Dermatitis :: necrolytic migratory erythema
  • Diabetes
  • Deep vein thrombosis (DVT)

Whipple Triad of Insulinoma

  • Symptoms of hypoglycemia
  • Fasting hypoglycemia :: < 50 mg/dL
  • Relief of symptoms on IV glucose

Diagnosis of Diabetes Mellitus

Diagnosis FBG OGTT HbA1c
Normal < 100 mg/dL 50-g 1-hour < 140 mg/dL < 6.5%
Gestational < 125 mg/dL 50-g 1-hour > 140 mg/dL
100-g 3-hour ≥ 2/4
-
Overt > 125 mg/dL 75-g 2-hour > 200 mg/dL > 6.5%

Medications for Diabetes Mellitus

Mechanism Effects Medication Indications
Insulin ↑ Insulin Rapid acting:
Lispro
Aspart
Glulisine
DM
    Short acting:
Regular insulin
DM
    Intermediate acting:
NPH insulin
DM
    Long acting:
Glargine
Detemir
DM
K channel blockers ↑ Insulin 1° Sulfonylureas:
Tolbutamide
Chlorpropamide
DM type 2
    2° Sulfonylureas:
Glimepiride
Glipizide
Glyburide
DM type 2
    Meglitinides [-Glinides] DM type 2
DPP-4 inhibitors ↑ Insulin
↓ Glucagon
-Gliptins DM type 2
GLP-1 analogs ↑ Insulin
↓ Glucagon
Exenatide
Liraglutide
Semaglutide
DM type 2
Amylin analogs ↓ Glucagon Pramlintide DM
α-Glucosidase inhibitors ↓ Glucose Acarbose
Miglitol
DM type 2
SGLT-2 inhibitors ↓ Glucose -Gliflozins DM type 2
AMPK inducers ↑ Insulin sensitivity Biguanides:
Metformin
DM type 2
PPAR-γ inducers ↑ Insulin sensitivity Thiazolidinediones [-Glitazones] DM type 2

Treatment of Acute Hyperglycemia

  • Fluids :: isotonic saline
  • Potassium
  • Insulin
  • Bicarbonate if indicated
  • Phosphate if indicated

Microvascular Complications of Diabetes Mellitus

  • Retinopathy
  • Nephropathy
  • Neuropathy

Insensitivity of Endocrine Receptors

Receptor Disease
GH Laron syndrome
PTH Pseudohypoparathyroidism (PHP)
LH & FSH Resistant ovary [Savage] syndrome
Androgen Androgen insensitive syndrome (AIS)
Insulin Diabetes mellitus type 2
Vasopressin Nephrogenic diabetes insipidus (DI)

Endocrine Tests

Test Indication Positive Negative
GH stimulation test ↓ Pituitary Hypopituitarism -
GnRH stimulation test ↓ Pituitary Hypopituitarism -
  Precocious puberty Peripheral precocious puberty Central precocious puberty
Progestin challenge test 2° Amenorrhea Non-anovulation Anovulation
TRH stimulation test ↓ Pituitary Hypopituitarism -
ACTH stimulation test ↓ Cortisol 1° Adrenal insufficiency 2° Adrenal insufficiency
Dexamethasone suppression test :: low-dose ↑ Cortisol Cushing syndrome -
Dexamethasone suppression test :: high-dose ACTH-dependent Cushing syndrome Ectopic ACTH Cushing disease
Saline suppression test ↑ Aldosterone 1° Hyperaldosteronism -
Oral glucose tolerance test ↑ Glucose Diabetes mellitus -
Water deprivation test Polyuria Diabetes insipidus Polydipsia
Desmopressin challenge test Diabetes insipidus Nephrogenic DI Central DI

Neuroendocrine Tumors (NET)

Ectodermal Origin

Origin Tumors
Surface ectoderm Craniopharyngioma
Pituitary adenoma
Neuroectoderm ::
neural tube
Pinealoma
Neuroectoderm ::
neural crest
Pheochromocytoma
Paraganglioma

Endodermal Orign

  • Medullary thyroid carcinoma
  • Parathyroid tumors
  • Carcinoid tumors
  • Gastrinoma
  • VIPoma
  • Insulinoma
  • Glucagonoma
  • Small cell carcinoma
  • Large cell carcinoma

Multiple Endocrine Neoplasias (MEN)

MEN Type 1

  • Pituitary adenoma
  • Parathyroid tumors
  • Pancreatic endocrine tumors

MEN Type 2A

  • Parathyroid tumors
  • Medullary thyroid carcinoma
  • Pheochromocytoma

MEN Type 2B

  • Medullary thyroid carcinoma
  • Pheochromocytoma
  • Mucosal neuroma