Thyroid Disorders

The thyroid gland in the neck makes hormones that set the body’s metabolic rate, which governs how energy is produced or stored and how waste products are removed. Thyroid hormone levels affect the behaviour of all cells and organs in the body, including the ovaries and testes. Thyroid disorders can be a crucial issue for couples who have difficulty conceiving

“because of its significant, frequent and often reversible or preventable effect on infertility” ⁱ

Thyroid hormones regulate the function of all cells and are particularly important for controlling:

• Energy requirements and the metabolic rate
• Protein production and regulation
• Cholesterol production and regulation
• Sensitivity to other hormones
• The use of vitamins, carbohydrates, fats, electrolytes
• The growth and function of multiple systems in the body
• Aspects of heart functions

The thyroid loop

The thyroid is part of the hypothalamic-pituitary-thyroid (HPT) axis, and the glands in the axis work in a sequence to manage the metabolism with thyroid hormones:Mikael Häggström

1. The hypothalamus releases thyrotropin-releasing hormone (TRH), which stimulates the pituitary to produce TSH. (High levels of TRH can also stimulate the pituitary to produce ‘prolactin’ and stop menstrual cycles: hyperprolactinaemia)
2. The pituitary produces thyroid-stimulating hormone (TSH) (also called thyrotropin), which stimulates the thyroid to produce thyroid hormones
3. The thyroid produces a variety of thyroid hormones (T₁– T₄)

When the thyroid hormones reach the right level, they stop the hypothalamus from producing further TRH (and overheating the body) in a ‘negative feedback system’ similar to how the menstrual cycle works.

Thyroid hormones

Thyroid hormones vary according to the number of iodine molecules attached to them, which also affects how long they last in the body, and how biologically active they are, and T₄ (thyroxine) is usually used as the marker for all of the thyroid hormones.

• T₄ : 80% (Thyroxine) is the most common hormone
• T₃ : 15% (Triiodothyronine) is less common but about four times more “biologically active” than T₄ (particularly for the liver and brain)
• T₂ : 3%
• T₁ : 1%

T₃ is made in two ways; either directly by the thyroid gland, or it’s converted from T₄ when an iodine molecule is removed. Some people make sufficient T₄ but aren’t good at converting it to T_3, which is the most powerful type. A “Reverse T₃” hormone also exists, and this is crucial for some people, and the issues of conversion from T₄ can be due to a lack of micronutrients in the diet.

All hormones have a “half-life”, which is how long they last before half of them degenerate:

• T₄ has a half-life of 7 days
• T₃ has a half-life of 1 day
• TSH has a half-life of less than 1 hour ⁱⁱ

Thyroid disorders

There are two types of thyroid disorders (either over-or under-active), and the imbalances can be either overt or subclinical:

1. ‘Overt’ is the more extreme (and universally accepted form) where both TSH and T₄ levels are abnormal
2. ‘Subclinical’ is when T₄ levels are normal, but TSH is abnormal

• • Overt Hyperthyroid has low TSH and raised T₄ levels
  • Subclinical Hyperthyroid is milder: TSH is low, but T₄ levels are normal
    • Overt Hypothyroid has raised TSH and low T₃ and T₄ levels
    • Subclinical Hypothyroid is milder: TSH is high, but T₄ levels are normal ⁱⁱⁱ

Although subclinical hypothyroidism has normal T₄ levels, there are problems with TSH production, and clinical outcomes can be very similar to the overt form. This is particularly important for women trying (or pregnant) as low TSH affects the chances of miscarriage and children’s health.

1. Hyperthyroid (overactive)

The thyroid is producing excessive thyroid hormones in response to the level of stimulation it gets from TSH. For women, the symptoms are:

• Oligomenorrhea (no periods)
• Anovulation (not ovulating)
• Increased bleeding (rare)

2. Hypothyroid (underactive)

The thyroid gland isn’t producing enough thyroid hormone relative to the stimulation it gets from TSH. The symptoms for women are:

• Anovulation
• Abnormal menstrual cycles (usually with heavy periods)
• An increased chance of miscarriage and complications for the baby
• Puberty may be disrupted

Thyroid testing

Thyroid testing measures TSH and thyroid hormones, and it’s not unusual for T₄ to be the only thyroid hormone tested; however, there are tests that include T₃ and reverse T₃.

We recommend you get a Thyroid Function & Autoimmune Reaction Home Test Kit to see if you are affected by thyroid problems.

It’s possible to test thyroid hormones with urine samples, and children or pregnant women are recommended to use urine iodine concentration (UIC) tests. Thyroid hormone production varies dramatically across the day, and levels are often twice as high at the night as in the afternoon and the most accurate time to take readings is in the morning. ^iv

For more information, see symptoms, references and risk factors and hypothyroidism and infertility.