What happens when thyroxine increases?

When thyroxine (T4) increases, it leads to:

1. Increased metabolic rate:

- Thyroxine promotes the activity of the sodium-potassium pump, which results in increased ion movement and energy expenditure.

- It stimulates the synthesis of various enzymes involved in metabolic pathways, leading to higher energy consumption at the cellular level.

2. Increased protein synthesis:

- Thyroxine enhances the synthesis of messenger RNA (mRNA) and ribosomes, which contributes to increased production of proteins.

- This higher protein production results in increased enzyme activity and overall enhanced cellular function.

3. Increased oxygen consumption and heat production:

- The increased metabolic rate and cellular activity lead to higher oxygen consumption by cells.

- As more energy is generated, there is an increase in heat production, contributing to the regulation of body temperature.

4. Weight loss:

- Due to the increased energy expenditure, individuals with higher thyroxine levels often experience weight loss.

5. Faster heart rate and cardiac output:

- Thyroxine stimulates the heart rate, leading to a faster pulse.

- Increased cardiac output ensures adequate circulation to meet the higher oxygen demand of tissues.

6. Enhanced gastrointestinal motility:

- Increased thyroxine levels promote faster movement of food through the digestive tract, leading to more frequent bowel movements.

7. Changes in mood and behavior:

- In general, higher thyroxine levels can cause heightened emotional states, increased energy levels, nervousness, anxiety, and a tendency towards irritability or emotional instability.

8. Reproductive effects:

- In women, elevated thyroxine levels may affect menstrual cycles, causing irregularities or even temporary amenorrhea (absence of menstruation).

- In men, very high thyroxine levels can potentially affect sperm production and fertility.

9. Bone metabolism:

- Thyroxine plays a role in bone remodeling and mineralization. Extended periods of elevated thyroxine levels can lead to increased bone resorption, which may contribute to the development of osteoporosis.

It's important to note that the above effects occur when thyroxine levels are significantly elevated or in cases of thyrotoxicosis, where the thyroid gland is overactive and producing too much thyroxine. Normal variations within the reference range of thyroxine levels do not typically cause noticeable changes.