Pituitary Hypothyroidism Causes

[Blossom Stemmer]

The thyroid gland is an important organ of the endocrine system, located in the front of the neck just below the voicebox. The thyroid secretes the hormones thyroxine (T4), triiodothyronine (T3), and calcitonin, which control body metabolism and regulate calcium balance. The secretion of T3 and T4 by the thyroid is controlled by an endocrine feedback system involving the pituitary gland and the hypothalamus (structures in the brain). Lowered levels of these thyroid hormones result in increased levels of pituitary and hypothalamic hormones. The reverse is also true -- when levels of the thyroid hormones rise, pituitary and hypothalamic hormones fall back. This helps keep levels appropriately balanced.

Since the thyroid gland is regulated by the pituitary gland and the hypothalamus, thyroid disorders may result not only from defects in the thyroid itself but also from the disruption of the control system in these other organs. Thyroid disorders caused by overproduction of thyroid hormones are called hyperthyroidism, and underproduction of these hormones is known as hypothyroidism.

The cause of secondary hypothyroidism is failure of the pituitary gland to secrete thyroid stimulating hormone (TSH). This is usually caused by a tumor in the region of the pituitary. Rarely the cause is an infiltration of the pituitary by inflammatory cells from the immune system or foreign substances (such as iron in hemochromotosis). Hypothyroidism may cause a variety of symptoms and can affect all body functions. The body's normal rate of functioning slows, causing mental and physical sluggishness. Symptoms vary from mild to severe. The most severe form is called myxedema, which is a medical emergency and can lead to coma and death.

A physical exam usually reveals a small thyroid gland. Vital signs (temperature, pulse, rate of breathing, blood pressure) reveal a slow heart rate, low blood pressure, and low temperature. A chest x-ray may reveal an enlarged heart. Laboratory tests to determine thyroid function include:

The purpose of treatment is to replace the deficient thyroid hormone. Levothyroxine is the most commonly used medication. The lowest dose effective in normalizing thyroid function is used. Life-long therapy may be necessary. Medication must be continued even when symptoms subside. After replacement therapy has begun, report any symptoms of increased thyroid activity (hyperthyroidism), such as restlessness, rapid weight loss, and sweating.

A high-fiber, low-calorie diet and moderate activity will help relieve constipation and promote weight loss if weight was gained during the time when thyroid activity was low. In individuals with accompanying hypoadrenalism, steroid replacement must be instituted before thyroid replacement is begun. In patients who have hypothyroidism caused by a pituitary tumor, surgery may be required. However, surgery may not cure the hypothyroidism, and thyroid replacement will still be needed.

Myxedema coma is treated by intravenous (IV) thyroid replacement and steroid therapy. Supportive therapy of oxygen, assisted ventilation, fluid replacement, and intensive care nursing may be indicated.

Calling your health care provider:

Call your health care provider if signs of hypothyroidism are present, or if chest pain or rapid heartbeat occur. Call your provider if restlessness, rapid weight loss, sweating, or other symptoms occur after beginning treatment for this disorder. Call your provider if headache, visual loss, or breast discharge occur.

At its most severe, undiagnosed hypothyroidism can manifest as myxedema. This life-threatening condition is characterized by swelling, slowed heart rate, low blood pressure, confusion, low body temperature, and fluid buildup around the heart. It requires hospitalization for urgent treatment.

The pituitary gland is responsible for secreting hormones that interact with the kidneys, sex glands, adrenal glands, and thyroid gland. With pituitary gland failure, symptoms include fatigue, low blood pressure, irregular or absent menstrual cycles, infertility, decreased libido, mood changes, weight changes, muscle weakness, and skin, hair, and nail changes.

In primary hypothyroidism, a problem involving the thyroid gland itself, the pituitary gland can become enlarged due to enlargement (hyperplasia) of cells that secrete thyroid stimulating hormone (TSH). This is because there is excess thyrotropin stimulating hormone, which tells the pituitary gland to secrete TSH to normalize thyroid levels.

Pituitary hypothyroidism is diagnosed using laboratory tests for thyroid hormone levels (T3 and T4) as well as thyroid stimulating hormone (TSH) levels. Low T3 and T4 levels with normal or low TSH levels indicate a problem with the brain. A brain MRI is needed for further evaluation.

Dr. Kelly Wood is an ABMS board certified endocrinologist and internal medicine physician who treats adults with diabetes, thyroid disease, osteoporosis, and other hormonal conditions. She achieved her fellowship in endocrinology from University of Wisconsin Hospital and Clinics.

Heather Hobbs (she/her) is an editor at Healthline Media and RVO Health. She has also worked in content creation, marketing, copy editing, and search engine optimization (SEO) for brands, agencies, and nonprofit organizations. A former educator, she earned her MA in teaching as well as a BA with a double major in English writing and Spanish, along with a minor in French. You can find her on LinkedIn.

A problem with any of these three glands can lead to hypothyroidism. The vast majority of hypothyroidism diagnoses are caused by problems with the thyroid gland and are categorized as primary hypothyroidism.

To diagnose pituitary hypothyroidism, a doctor will likely start by asking about your symptoms and reviewing your personal and family medical history. They may perform a physical exam where they feel your thyroid gland for abnormal changes.

For example, some people may also have secondary adrenal insufficiency that may require glucocorticoid treatment. Secondary adrenal insufficiency is when your pituitary gland does not produce enough adrenocorticotropic hormone (ACTH), which leads to low cortisol levels.

Secondary hypothyroidism is a rare form of hypothyroidism caused by your pituitary gland underproducing TSH. It makes up less than 1% of cases of hypothyroidism and can cause symptoms like fatigue, poor cold tolerance, and weight gain.

The pituitary gland is a kidney-bean-sized gland at the base of your brain. It is part of the body's system of glands that make hormones, called the endocrine system. The pituitary gland makes several hormones. They act on nearly every part of the body.

The endocrine system is made up of glands and organs that make hormones. The endocrine system includes the pituitary gland, thyroid gland, parathyroid glands, adrenal glands, pancreas, ovaries and testicles.

Hypopituitarism is when there isn't enough of one or more of the pituitary hormones. This lack of hormones, called a deficiency, can affect how the body works in many ways. These include growth, blood pressure and the ability to have children, among others. Symptoms depend on which hormones are missing.

Symptoms of hypopituitarism vary from person to person. Symptoms depend on what hormones are missing and how little of the hormone is being made. There might be more than one hormone that's low. A second hormone deficiency might increase the symptoms of the first one. Or sometimes, it might hide those symptoms.

Contact your health care provider right away if symptoms of hypopituitarism start suddenly or come with a bad headache, changes in vision, confusion or a drop in blood pressure. These could be symptoms of sudden damage to the pituitary gland tissue. This condition is known as pituitary apoplexy.

Hypopituitarism has a number of causes. One common cause is a tumor of the pituitary gland. As a pituitary tumor grows, it can press on and damage pituitary tissue. This disrupts the pituitary gland's ability to make hormones. A tumor also can press on the optic nerves, causing vision problems.

In some cases, a change in a gene causes hypopituitarism. That change is heredity, which means it is passed down in families. The genetic change affects the pituitary gland's ability to make one or more of its hormones. This often starts at birth or in early childhood.

Tumors or diseases of a part of the brain that's just above the pituitary, called the hypothalamus, also can cause hypopituitarism. The hypothalamus makes hormones that affect how the pituitary gland works.

Hypothyroidism is caused by a deficiency in the production of thyroid hormone and may be either primary or secondary. Primary hypothyroidism occurs when the thyroid gland does not make sufficient amounts of thyroid hormone. It is usually characterized by high levels of thyroid-stimulating hormone (TSH) and low levels of the thyroid hormones triiodothryronine (T3) and tetraiodothryonine (T4).

Secondary (or central) hypothyroidism is caused by disorders of the pituitary gland or hypothalamus. Generally, secondary hypothyroidism is associated with low TSH and low T3 and T4. However, TSH levels may also be normal or even slightly elevated. For this reason, TSH is often an unreliable measure of secondary hypothyroidism and should not be used to assess the adequacy of thyroid replacement in these patients.

Thyroid hormone deficiency causes mental retardation in infants, growth delay in children, and myxedema in adults. Symptoms of thyroid hormone insufficiency include cold intolerance, weight gain, memory loss, dry skin, hair loss, brittle nails, constipation, increased sleep demand, and fatigue. Severe hypothyroidism left untreated can lead to coma and even death.

Hypothyroidism from TSH or TRH deficiency can result from hypothalamic or pituitary destruction (neoplastic, inflammatory, granulomatous, vascular, traumatic, autoimmune, and radiation necrosis). Typically, loss of TSH secretion is associated with other hormonal abnormalities because there is a step-wise loss of pituitary function starting with growth hormone, gonadotropins, and then thyrotropin (lastly ACTH) in the presence of an expanding pituitary tumor.

3a8082e126