Hyperthyroidism: Pathology review

On the Endocrinology ward, two individuals came in.

The first one is 55 year old Gregor, who came in complaining about weight loss, heat intolerance, chest pain, palpitations and insomnia.

On the clinical examination, he’s anxious and restless.

He had warm and moist skin, his eyelids were retracted and there was exophthalmos of both eyes and tachycardia.

The other person is 37 year old Josie who migrated to the US from Panama.

She came in with similar symptoms as Gregor but on clinical examination, she also had a goiter.

According to her, she recently had a contrast imaging procedure for a different problem.

TSH and levels of T3 and T4 were taken for both individuals.

Levels of TSH were low, while levels of T3 and T4 were high.

Okay, so both individuals had hyperthyroidism.

First, a bit of physiology.

Normally, the hypothalamus detects low blood levels of thyroid hormones and releases thyrotropin-releasing hormone, or TRH, into the hypophyseal portal system.

The anterior pituitary then releases thyroid-stimulating hormone, also called thyrotropin, or simply TSH.

TSH stimulates the thyroid gland which is a gland located in the neck.

The thyroid gland is made up of thousands of follicles, which are small spheres lined with follicular cells.

Follicular cells convert thyroglobulin, a protein found in follicles, into two iodine-containing hormones, triiodothyronine or T3, and thyroxine or T4.

Once released from the thyroid gland, these hormones enter the blood and bind to circulating plasma proteins.

Only a small amount of T3 and T4 will travel unbound in the blood, and these two hormones get picked up by nearly every cell in the body.

Once inside the cell T­4 is mostly converted into T3, and it can exert its effect. T3 speeds up the cell’s basal metabolic rate.

T3 increases cardiac output, stimulates bone resorption, thinning out the bones, and activates the sympathetic nervous system.

Thyroid hormones are also involved in a number of other things, like controlling sebaceous and sweat gland secretion, hair follicle growth, and regulating proteins and mucopolysaccharide synthesis by skin fibroblasts.