Thyroid Hormones, Hyperthyroidism, Hypothyroidism, Symptoms, Treatment and Brand Generic Drugs

Thyroid Gland

The thyroid is a butterfly-shaped endocrine gland located in the anterior neck (below the larynx, spanning the trachea). It produces hormones that regulate:

Metabolism (energy use)
Growth & development
Body temperature
Heart & nervous system function

Thyroid Hormone

There are three main types of thyroid hormones, but two of them are the most biologically important. Here’s a breakdown:

1. Classic Thyroid Hormones (Regulate Metabolism)

Hormone	Full Name	Key Features
T4	Thyroxine (Tetraidothyronine)	– Major secreted hormone (90%) – Prohormone: Converted to T3 in tissues – Long half-life (~7 days)
T3	Triiodothyronine	– Biologically active form (3–4x more potent than T4) – Only 10% secreted directly; rest comes from T4 conversion – Short half-life (~1 day)

2. Additional Thyroid Hormone (Calcium Regulation)

Hormone	Full Name	Key Features
Calcitonin	–	– Produced by C-cells (parafollicular cells) in thyroid – Lowers blood calcium (inhibits osteoclasts) – Minor role compared to PTH (parathyroid hormone)

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1. T4 – Thyroxine

Most abundant thyroid hormone (~90%)
Inactive form, acts as a storage hormone
Converted to T3 in the body’s tissues
Function: Precursor to T3; maintains steady levels

2. T3 – Triiodothyronine

Active form of thyroid hormone
More potent than T4 (3–5x stronger)
Only about 10% made by thyroid, most is converted from T4
Function: Controls metabolism, heart rate, body temperature, brain function, and more

3. Calcitonin

Produced by the C cells (parafollicular cells) of the thyroid
Unrelated to T3/T4, but still a thyroid hormone
Function: Lowers blood calcium levels (minor role in calcium balance compared to parathyroid hormone)

Easy Comparison

Hormone	Full Name	Role	Activity
T4	Thyroxine	Storage hormone	Inactive
T3	Triiodothyronine	Main active form	Active
Calcitonin	—	Lowers calcium	Active (minor role)

Hormone Production Pathway

Hypothalamus → TRH → Pituitary → TSH → Thyroid → T3 and T4

TRH (Thyrotropin-Releasing Hormone) – from hypothalamus

TSH (Thyroid-Stimulating Hormone) – from pituitary

T3/T4 – from thyroid gland

Thyroid Hormone Synthesis Pathway

Hypothalamus TRH (Thyrotropin-releasing hormone)

→

Pituitary TSH (Thyroid-stimulating hormone)

→

Thyroid T3 and T4

Click each step to view more details about each process.

Step-by-Step Explanation of the Thyroid Hormone Regulation Pathway:

Hypothalamus (in the brain):

This part of your brain acts like a command center. It monitors your body’s needs and starts the process when more thyroid hormones are required.

👉 Hypothalamus releases a hormone called TRH (Thyrotropin-Releasing Hormone).

TRH travels to the Pituitary Gland (also in the brain):

The pituitary gland is like a messenger station that gets signals from the hypothalamus and then tells other glands what to do.

👉 In response to TRH, the pituitary gland releases TSH (Thyroid-Stimulating Hormone).

TSH travels through the blood to the Thyroid Gland (in your neck):

Now the message reaches the thyroid gland, telling it to make and release thyroid hormones.

👉 The thyroid responds by producing T4 (thyroxine) and a smaller amount of T3 (triiodothyronine).

T4 is converted to T3 in tissues:

T4 is the storage or inactive form. In various body tissues (like the liver and kidneys), it’s converted to T3, which is the active form that controls metabolism and energy use.

Your body now has the right amount of T3 and T4 circulating to regulate important functions like:

Metabolism
Heart rate
Temperature
Energy levels
Growth and development

Functions of Thyroid Hormones:

Metabolic rate – ↑ Basal metabolic rate (BMR)
Thermogenesis – Maintains body temperature
Growth & development – Essential for brain development in infants
Cardiovascular – ↑ Heart rate and cardiac output
GI function – ↑ Motility
Lipid and glucose metabolism – Enhances lipolysis, glycogenolysis
Mood and cognition – Affects mental status and energy levels

Role of TSH (Thyroid-Stimulating Hormone)

TSH (Thyroid-Stimulating Hormone), also called thyrotropin, is a pituitary hormone that regulates thyroid function. It is the key controller of thyroid hormone production and release.

1. Primary Functions of TSH

A. Stimulates Thyroid Hormone Production

Triggers T4/T3 Synthesis: TSH binds to receptors on thyroid follicular cells, activating:
Iodine uptake (via sodium-iodide symporter, NIS).
Thyroglobulin (Tg) production.
Enzymes for T4/T3 formation (thyroid peroxidase, TPO).

B. Promotes Thyroid Growth

Chronic TSH stimulation → thyroid enlargement (goiter).

C. Maintains Feedback Balance

Low T4/T3 → TSH rises (signals thyroid to work harder).
High T4/T3 → TSH falls (prevents overproduction).

2. Clinical Significance of TSH

A. Diagnostic Marker

First-line test for thyroid disorders:
- High TSH = Hypothyroidism (underactive thyroid).
- Low TSH = Hyperthyroidism (overactive thyroid).
B. Guides Treatment
- Hypothyroidism: Goal is to normalize TSH with levothyroxine (T4).
- Hyperthyroidism: Goal is to suppress TSH (with antithyroid drugs/surgery).

HYPERTHYROIDISM

(“Hyper” = too much)

What is Hyperthyroidism?

A condition where the thyroid gland produces too much T3 and T4 hormones, leading to an overactive metabolism.

Hyperthyroidism Causes:

Graves’ Disease – autoimmune (most common cause)
Toxic multinodular goiter
Thyroid adenoma (benign tumor)
Thyroiditis (inflammation)
Excess iodine intake or overuse of thyroid meds

Symptoms of Hyperthyroidism:

Metabolism: Weight loss despite increased appetite
Cardiovascular: Fast heart rate (tachycardia), palpitations
Nervous: Anxiety, restlessness, irritability, tremors
Skin: Warm, moist skin, sweating, hair thinning
GI: Frequent bowel movements, diarrhea
Eyes: Bulging eyes (exophthalmos) in Graves’ disease
Menstrual: Irregular or lighter periods
Others: Heat intolerance, insomnia, fatigue

HYPORTHYROIDISM

(“Hypo” = too little)

What is Hypothyroidism?

A condition where the thyroid gland doesn’t produce enough T3 and T4, causing a slowed metabolism.

Causes of Hypothyroidism:

Hashimoto’s Thyroiditis – autoimmune (most common)
Iodine deficiency
Thyroid surgery or radiation
Medications (e.g., lithium, amiodarone)
Congenital hypothyroidism

Symptoms of Hypothyroidism:

Metabolism: Weight gain despite poor appetite
Cardiovascular: Slow heart rate (bradycardia)
Nervous: Depression, fatigue, poor memory
Skin: Dry, coarse skin, cold intolerance
GI: Constipation
Hair: Hair thinning or hair loss, brittle nails
Menstrual: Heavy or irregular periods
Others: Puffy face, hoarseness, low energy, slow reflexes

Hypothyroidism vs Hyperthyroidism

Feature	Hyperthyroidism	Hypothyroidism
Hormone levels	↑ T3, T4	↓ T3, T4
Weight	Loss	Gain
Energy	Anxious, restless	Tired, sluggish
Heart Rate	Fast (↑)	Slow (↓)
Temperature Tolerance	Heat intolerance	Cold intolerance
GI symptoms	Diarrhea	Constipation
Skin	Moist, warm	Dry, coarse
Hair	Fine hair, hair loss	Thinning hair, brittle
Eyes	Bulging (in Graves’)	Puffy face
Mood	Irritable, nervous	Depressed, slow thinking

Mnemonics for Thyroid Symptoms

Mnemonics for Hypothyroidism (Underactive Thyroid) – “SLOWED”

S – Sluggish (fatigue, lethargy)
L – Low heart rate (bradycardia)
O – Overweight (weight gain)
W – Weakness (muscle aches)
E – Edema (puffy face, myxedema)
D – Depression & Dry skin

(Other symptoms: Cold intolerance, constipation, thinning hair, hoarse voice, heavy periods.)

Mnemonics for Hyperthyroidism (Overactive Thyroid) – “FAST”

F – Feverish (heat intolerance)
A – Anxious (nervousness, irritability)
S – Sweating & Skin thinning
T – Tachycardia (rapid heart rate) & Tremors

(Other symptoms: Weight loss, diarrhea, bulging eyes (exophthalmos in Graves’ disease), insomnia, muscle weakness.)

Bonus Contrast Mnemonic:

Hypothyroidism = “Everything is SLOW” (cold, tired, constipated, gaining weight).
Hyperthyroidism = “Everything is FAST” (hot, anxious, diarrhea, losing weight).

Thyroid Test & Lab Values

Thyroid tests measure hormone levels to diagnose hypothyroidism, hyperthyroidism, and other thyroid disorders. Here’s a breakdown of key tests, their normal ranges, and interpretations.

1. Primary Thyroid Hormones

Test	Normal Range	Hyperthyroidism	Hypothyroidism	What It Measures
TSH (Thyroid-Stimulating Hormone)	0.4–4.0 mIU/L	↓ Low (<0.1)	↑ High (>10)	Pituitary hormone that regulates T4/T3 production
Free T4 (Thyroxine)	0.8–1.8 ng/dL	↑ High (>1.8)	↓ Low (<0.8)	Active form of thyroxine (major thyroid hormone)
Free T3 (Triiodothyronine)	2.3–4.2 pg/mL	↑ High (>4.2)	Normal or ↓ Low	More potent but short-lived thyroid hormone

Hyperthyroidism: Low TSH + High T4/T3
Hypothyroidism: High TSH + Low T4

Why Free T4 & Free T3?

“Free” = Bioavailable (not protein-bound).
More accurate than Total T4/T3 (affected by pregnancy, medications, liver disease).

2. Thyroid Antibodies (Autoimmune Testing)

Test	Significance
TPO Antibodies (Thyroid Peroxidase)	Elevated in Hashimoto’s thyroiditis (hypothyroidism)
TRAb (TSH Receptor Antibodies)	Elevated in Graves’ disease (hyperthyroidism)
Thyroglobulin Antibodies	Seen in Hashimoto’s or thyroid cancer monitoring

Interpreting Thyroid Lab Results

A. Hypothyroidism (Underactive Thyroid)

Primary Hypothyroidism (Most Common):

↑ TSH (High)
↓ Free T4 (Low)
Cause: Hashimoto’s (check TPO antibodies), iodine deficiency, thyroid surgery.

Secondary Hypothyroidism (Rare – Pituitary Issue):

↓ or Normal TSH
↓ Free T4

B. Hyperthyroidism (Overactive Thyroid)

Primary Hyperthyroidism:

↓ TSH (Low or Suppressed)
↑ Free T4 and/or Free T3
Cause: Graves’ disease (check TRAb), toxic nodules, thyroiditis.

Subclinical Hyperthyroidism:

↓ TSH (Low)
Normal Free T4 & T3

C. Euthyroid Sick Syndrome (Non-Thyroidal Illness)

Low T3, Normal/Low T4, Normal/High TSH
Seen in critically ill patients (not a true thyroid disorder).

Thyroid Lab Interpretation Table

Condition	TSH	Free T4	Free T3	Antibodies
Primary Hypo	↑↑	↓	Normal/↓	TPO (+)
Primary Hyper	↓↓	↑	↑	TRAb (+) (Graves’)
Subclinical Hypo	↑	Normal	Normal	–
Subclinical Hyper	↓	Normal	Normal	–
Thyroiditis	Varies	Varies	Varies	TPO/TRAb (+)

Thyroid Medications (Treatment)

Brand Name	Generic Name	Mechanism of Action	Used For	Important points
Synthroid, Levoxyl, Euthyrox, Unithroid	Levothyroxine sodium	Synthetic T4; converts to T3 in the body to regulate metabolism	Hypothyroidism	Gold standard for hypothyroidism. Must take on empty stomach Avoid food or coffee for at least 2 hours. Avoid calcium/iron supplements within 2-3 hours.
Cytomel	Liothyronine sodium	Synthetic T3; directly active thyroid hormone	Hypothyroidism	Short-acting, rarely used alone Short half-life (must dose 2–3x/day). Sometimes combined with T4 (e.g., Thyrolar). Risk of cardiac strain if overused.
Armour Thyroid, NP Thyroid, Nature-Throid	Desiccated thyroid (USP)	Natural T4 & T3 combination from porcine thyroid glands	Hypothyroidism	Contains T4 + T3 (from pig thyroid). Not first-line (inconsistent potency). Some patients prefer it despite guidelines.
Tapazole	Methimazole	Inhibits thyroid peroxidase enzyme; blocks T4/T3 synthesis	Hyperthyroidism	Blocks thyroid peroxidase (TPO). Avoid in 1st trimester pregnancy (use PTU). check CBC if fever/sore throat, liver toxicity.
(No brand; generic only)	Propylthiouracil (PTU)	Inhibits T4/T3 synthesis and blocks peripheral conversion of T4 to T3	Hyperthyroidism (esp. in pregnancy)	Used in 1st trimester (less placental transfer). Higher liver toxicity risk than methimazole. Also inhibits T4→T3 conversion (useful in thyroid storm).
(No brand; radioactive isotope)	Radioactive Iodine (I-131)	Destroys overactive thyroid tissue via radiation (may cause permanent hypothyroidism).	Hyperthyroidism, Thyroid Cancer Graves’ disease, toxic nodules.	Post-Treatment: Monitor TSH, start levothyroxine if needed.
No Brand	Potassium Iodide (Lugol’s Solution, SSKI)	High iodine inhibits thyroid hormone synthesis and release Shrinks the thyroid gland and reduces blood flow. Rapid reduction in T4/T3 levels.	Thyroid storm, pre-surgery (shrinks thyroid).	5% Iodine + 10% Potassium Iodide in water. Do not use alone in hyperthyroidism (must pair with methimazole/PTU) Not for long-term use
Inderal	Propranolol	Non-selective beta-blocker; reduces symptoms like tremors, palpitations	Symptom control in hyperthyroidism	Controls symptoms Controls tachycardia, tremors, anxiety.
Tenormin	Atenolol	Beta-1 selective blocker; reduces heart rate and tremors	Symptom control in hyperthyroidism	Symptoms management Tachycardia (↓ heart rate), Palpitations, Tremors, Anxiety

Synthetic vs. Natural Thyroid Medications

Synthetic Thyroid Medications

(e.g., Levothyroxine/Synthroid, Liothyronine/Cytomel) Pros:

Consistent potency: Precise dosing (FDA-regulated).
T4-only (Levothyroxine): Mimics natural thyroid hormone conversion (T4→T3).
Guideline-recommended: First-line for hypothyroidism (AACE/ATA).
Fewer side effects: No risk of excess T3 (unlike natural desiccated thyroid).

Cons:

❌ Some patients report persistent symptoms (fatigue, brain fog) despite “normal” TSH.

❌ Requires peripheral conversion (T4→T3), which may be inefficient in some patients.

Why Patients Might Prefer Synthetic:

Trust in evidence-based medicine.
Prefer stability and predictability of lab-made hormones.

Natural Desiccated Thyroid (NDT)

(e.g., Armour Thyroid, NP Thyroid) Pros:

Contains both T4 + T3: May benefit patients with conversion issues.
Historical use: Used for decades before synthetic options.
Some patients report better symptom relief (energy, mood, weight).

Cons:

❌ Variable potency: Batch-to-batch differences (less regulated).

❌ Risk of excess T3: Can cause palpitations, anxiety, or bone loss.

❌ Not guideline-preferred: Limited evidence of superiority over levothyroxine.

Why Patients Might Prefer NDT:

Belief in “natural” therapies.
Frustration with ongoing symptoms on levothyroxine.
Anecdotal reports of improved well-being.

Why Some Patients Switch from Synthetic to Natural Thyroid Meds:

Persistent Symptoms
- Despite “normal” TSH, some patients feel better on NDT (possibly due to T3 content).
Conversion Issues
- Genetic variations (e.g., DIO2 gene) may impair T4→T3 conversion.
Distrust of Synthetic Drugs
- Preference for “whole gland” therapy.

Why Doctors Often Prefer Synthetic Thyroid Meds:

Predictable Dosing
- NDT’s T4:T3 ratio (4:1) doesn’t match human thyroid secretion (~14:1).
Safety Concerns
- Excess T3 in NDT may cause cardiac strain or osteoporosis.
Lack of Strong Evidence
- Most studies show no significant difference in outcomes vs. levothyroxine.

Who Might Benefit from Natural Thyroid?

Patients with documented T4→T3 conversion issues.
Those who fail levothyroxine monotherapy despite dose optimization.
Individuals who philosophically prefer natural treatments (after informed discussion).

Who Should Stick with Synthetic?
Newly diagnosed hypothyroidism (first-line).

Pregnant women (requires precise TSH control).
Cardiac patients (T3 in NDT can stress the heart).

Medical conditions & their treatments with thyroid medications

1. Hypothyroidism (Underactive Thyroid)

Causes: Hashimoto’s, thyroidectomy, iodine deficiency. Treatment:
First-line: Levothyroxine (Synthroid) – Replaces T4.
Dose: 1.6 mcg/kg/day (start low in elderly/cardiac patients).
Monitor: TSH every 6–8 weeks.

Alternative:

Liothyronine (Cytomel) – T3 replacement (rarely used alone).
Desiccated thyroid (Armour) – T4 + T3 combo (not guideline-preferred).

Key Points to Remember:

Take levothyroxine first thing in the morning on an empty stomach with plain water.
Do not eat or drink anything for at least 1.5 hrs before or after the medication.
Avoid calcium/iron supplements within 4 hours.

2. Hyperthyroidism (Overactive Thyroid)

Causes: Graves’ disease, toxic nodules, thyroiditis. Treatment:
First-line: Methimazole (Tapazole) – Blocks thyroid hormone synthesis.
Dose: 5–30 mg/day (taper to maintenance).
Avoid in 1st trimester pregnancy (use PTU instead).

Alternative: Propylthiouracil (PTU) – Blocks T4→T3 conversion.

Use: Thyroid storm, 1st-trimester pregnancy.

Key Points to Remember:

Monitor Free T4/T3 (TSH may lag).
Methimazole side effects: Agranulocytosis (check CBC if fever/sore throat).

3. Thyroid Storm (Life-Threatening Hyperthyroidism)

Treatment:

PTU (preferred over methimazole) – 200–300 mg every 6h.
Beta-blockers (Propranolol) – Controls heart rate.
Lugol’s solution/SSKI – Blocks hormone release (give after PTU).
Steroids (Hydrocortisone) – Inhibits T4→T3 conversion.

Key Points to Remember:

ICU admission required.
Avoid aspirin (risks T3 release).

4. Post-Thyroidectomy Management

For Cancer:

Levothyroxine at suppressive doses (TSH <0.1 mIU/L). For Benign Disease:
Levothyroxine replacement (goal TSH: 0.5–2.5 mIU/L).

Key Points to Remember:

Check calcium post-op (risk of hypoparathyroidism).

5. Subclinical Hypothyroidism (TSH ↑, Normal T4)

Treatment:

Treat if TSH >10 or symptomatic (fatigue, weight gain).
Levothyroxine (start 25–50 mcg/day).

Key Points to Remember:

Recheck TSH in 6–8 weeks.

6. Pregnancy & Thyroid Disorders

Hypothyroidism:

Increase levothyroxine dose by 25–30% (TSH goal: <2.5 mIU/L).

Hyperthyroidism:

1st trimester: PTU.
2nd/3rd trimester: Switch to methimazole.

Key Points to Remember:

Monitor TSH every 4 weeks.

7. Myxedema Coma (Severe Hypothyroidism)

Treatment:

IV Levothyroxine (300–500 mcg loading dose).
Liothyronine (T3) if critical (due to peripheral conversion impairment).
Glucocorticoids (for adrenal insufficiency risk).

Key Points to Remember:

Slow rewarming, avoid sedatives.

8. Thyroid Cancer (Post-Thyroidectomy)

Treatment:

Levothyroxine suppression therapy (TSH <0.1 mIU/L for high-risk cancer).
Radioactive iodine (I-131) – For residual/metastatic disease.

Key Points to Remember: Avoid thyroid hormone replacement before I-131 scanning.

Some common terms associated with Thyroid Medical Conditions

Thyroid Eye Disease (TED)

An autoimmune condition, often linked with Graves’ disease, where immune cells attack the tissues around the eyes.
Symptoms: Bulging eyes, dryness, redness, eye pain, double vision, swelling.

Thyroid Knot

Typically refers to a thyroid nodule—a lump or abnormal growth in the thyroid.
Can be benign or cancerous.
May cause visible swelling or be found incidentally.

Thyroid Storm

A rare, life-threatening complication of untreated or poorly managed hyperthyroidism.
Symptoms: High fever, rapid heart rate, agitation, delirium, vomiting, coma.
Requires emergency treatment.

Thyroiditis

Inflammation of the thyroid gland.
Types: Hashimoto’s (chronic), De Quervain’s (painful), postpartum, silent.
Can lead to hypothyroidism or hyperthyroidism, depending on the stage.

Thyrotoxicosis

A state of excess thyroid hormones in the body.
Can result from hyperthyroidism, thyroiditis, or excess hormone intake.
Symptoms: Weight loss, heat intolerance, tremors, palpitations, anxiety.

Thyroid Eye Disease Symptoms

Bulging/protruding eyes
Dry or watery eyes
Light sensitivity
Double vision
Eye pressure or pain
Eyelid retraction

Thyroid Goiter

An enlargement of the thyroid gland.
May occur with normal, low, or high thyroid hormone levels.
Can cause a visible neck swelling or pressure symptoms.

Thyroid Hair Loss

Common with both hypothyroidism and hyperthyroidism.
Hair becomes dry, brittle, and falls out easily.
Usually reversible with proper thyroid treatment.

Thyroid Belly

Refers to weight gain or bloating often associated with hypothyroidism.
Slowed metabolism leads to fat accumulation, especially around the abdomen.

Thyroid Rash

Rashes can occur with:
Autoimmune thyroid disease (e.g., Hashimoto’s, Graves’)
Medication side effects (e.g., methimazole allergy)
Skin changes from hormonal imbalances

Thyroid Cyst

A fluid-filled sac in the thyroid gland.
Usually benign and asymptomatic.
Large cysts may cause neck discomfort or swallowing issues.

Thyroid Bulging Eyes

Another name for exophthalmos, a hallmark of Graves’ disease / Thyroid Eye Disease.
Caused by inflammation and swelling in eye muscles and tissues behind the eyes.

Frequently asked Questions and Answers

What are the Best Foods for Thyroid Patients

For Hypothyroidism:

Fruits: Berries, apples, peaches, pears, grapes, citrus fruits, pineapple, bananas. Healthline
Non-starchy Vegetables: Greens, artichokes, zucchini, asparagus, carrots, peppers, spinach, mushrooms. Healthline
Starchy Vegetables: Sweet potatoes, potatoes, peas, butternut squash. Healthline
Lean Proteins: Fish, shellfish, eggs, turkey, chicken. Healthline
Healthy Fats: Olive oil, avocados, coconut oil, full-fat yogurt. Healthline

For Hyperthyroidism:

Foods rich in selenium (e.g., Brazil nuts), iron (e.g., leafy greens), calcium, and vitamin D may be beneficial.

Source

What Foods to Avoid with Thyroid Conditions

Hypothyroidism:

Fried fast foods, processed foods high in salt, sugary treats (pastries, cakes, cookies, ice cream), excessive alcohol.

Hyperthyroidism:

High-iodine foods, soy products, gluten, caffeine. Medical News Today

Source

Best Cream for Thyroid-Related Dry Skin

For very dry skin, thicker moisturizers or oils are recommended. Products containing ammonium lactate or urea can help dissolve dead skin and allow moisturizers to penetrate more effectively.

Does Biotin Affect the Thyroid?

Biotin does not affect thyroid hormone levels or thyroid function. However, high doses can interfere with laboratory tests, leading to inaccurate thyroid function results. It’s advisable to stop taking biotin at least two days before thyroid testing. Source

Causes of Thyroid Disease in Females

Autoimmune Diseases: Conditions like Hashimoto’s thyroiditis and Graves’ disease are more prevalent in women and can lead to hypothyroidism or hyperthyroidism.
Hormonal Changes: Pregnancy, menopause, and other hormonal fluctuations can increase the risk.
Iodine Deficiency: Essential for thyroid hormone production; deficiency can lead to hypothyroidism. Cleveland Clinic

What are the causes of thyroid cancer?

Genetic mutations
Radiation exposure (especially in childhood)
Family history of thyroid or other endocrine cancers
Iodine deficiency (linked to some types)
Certain inherited conditions like MEN syndrome

What are the causes of overactive thyroid (Hyperthyroidism)?

Graves’ disease (most common cause)
Thyroid nodules (toxic adenoma or multinodular goiter)
Thyroiditis (temporary release of stored hormones)
Excessive iodine intake
Overmedication with thyroid hormone

Does thyroid affect periods?

Yes.

Hypothyroidism: May cause heavy, irregular, or prolonged periods.
Hyperthyroidism: May cause light, infrequent, or missed periods.

Does thyroid affect blood pressure?

Yes.

Hypothyroidism: Can lead to high diastolic BP (bottom number).
Hyperthyroidism: May cause high systolic BP (top number), rapid heartbeat.

Is thyroid treatable?

Yes.

Most thyroid conditions (hypo-, hyperthyroidism, nodules, goiters) are treatable with medications, radioactive iodine, or surgery.
Even thyroid cancer, especially papillary type, is often highly treatable.

Does thyroid affect pregnancy?

Yes.

Untreated thyroid disorders can cause infertility, miscarriage, premature birth, and developmental issues in the baby.
Proper management is important before and during pregnancy.

Is thyroid a hereditary disease?

Partially, yes.

Conditions like Graves’ disease, Hashimoto’s, and some thyroid cancers can run in families.
A family history increases the risk but doesn’t guarantee disease.

Thyroid Hormones, Hyperthyroidism, Hypothyroidism, Symptoms, Treatment and Brand Generic Drugs

Table of Contents

Thyroid Gland

Thyroid Hormone

1. Classic Thyroid Hormones (Regulate Metabolism)

2. Additional Thyroid Hormone (Calcium Regulation)

PTCB Practice Questions

PTCB Flashcards

PTCB Calculations

PTCB Quiz

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1. T4 – Thyroxine

2. T3 – Triiodothyronine

3. Calcitonin

Hormone Production Pathway

Step-by-Step Explanation of the Thyroid Hormone Regulation Pathway:

Hypothalamus (in the brain):

TRH travels to the Pituitary Gland (also in the brain):

TSH travels through the blood to the Thyroid Gland (in your neck):

T4 is converted to T3 in tissues:

Functions of Thyroid Hormones:

Role of TSH (Thyroid-Stimulating Hormone)

1. Primary Functions of TSH

A. Stimulates Thyroid Hormone Production

B. Promotes Thyroid Growth

C. Maintains Feedback Balance

2. Clinical Significance of TSH

A. Diagnostic Marker

HYPERTHYROIDISM

What is Hyperthyroidism?

Hyperthyroidism Causes:

Symptoms of Hyperthyroidism:

HYPORTHYROIDISM

What is Hypothyroidism?

Causes of Hypothyroidism:

Symptoms of Hypothyroidism:

Hypothyroidism vs Hyperthyroidism

Mnemonics for Thyroid Symptoms

Mnemonics for Hypothyroidism (Underactive Thyroid) – “SLOWED”

Mnemonics for Hyperthyroidism (Overactive Thyroid) – “FAST”

Bonus Contrast Mnemonic:

Thyroid Test & Lab Values

1. Primary Thyroid Hormones

Why Free T4 & Free T3?

2. Thyroid Antibodies (Autoimmune Testing)

Interpreting Thyroid Lab Results

A. Hypothyroidism (Underactive Thyroid)

Primary Hypothyroidism (Most Common):

Secondary Hypothyroidism (Rare – Pituitary Issue):

B. Hyperthyroidism (Overactive Thyroid)

Primary Hyperthyroidism:

Subclinical Hyperthyroidism:

C. Euthyroid Sick Syndrome (Non-Thyroidal Illness)

Thyroid Lab Interpretation Table

Thyroid Medications (Treatment)

Synthetic vs. Natural Thyroid Medications

Synthetic Thyroid Medications

Why Patients Might Prefer Synthetic:

Natural Desiccated Thyroid (NDT)

Why Patients Might Prefer NDT:

Why Some Patients Switch from Synthetic to Natural Thyroid Meds:

Why Doctors Often Prefer Synthetic Thyroid Meds:

Who Might Benefit from Natural Thyroid?

Who Should Stick with Synthetic?Newly diagnosed hypothyroidism (first-line).

Medical conditions & their treatments with thyroid medications

1. Hypothyroidism (Underactive Thyroid)

2. Hyperthyroidism (Overactive Thyroid)

3. Thyroid Storm (Life-Threatening Hyperthyroidism)

4. Post-Thyroidectomy Management

5. Subclinical Hypothyroidism (TSH ↑, Normal T4)

6. Pregnancy & Thyroid Disorders

Hypothyroidism:

Hyperthyroidism:

7. Myxedema Coma (Severe Hypothyroidism)

8. Thyroid Cancer (Post-Thyroidectomy)

Some common terms associated with Thyroid Medical Conditions

Thyroid Eye Disease (TED)

Thyroid Knot

Who Should Stick with Synthetic?
Newly diagnosed hypothyroidism (first-line).